# Inch ball bearings R-series: R188, R144, R166, R2, R3, R4, R6 to R24: bore, OD, width, r + 22 ring-envelope STEP/STL files (1/8 to 1-1/2 in bore)

> What are the dimensions of an R188, R144, R166, R2, R3, R4, R6 or R8 inch ball bearing: bore, OD and width, with and without shields?

- Category: Hardware › Bearings, rails & motion
- Kind: Standard part
- Basis: NSK inch-series table (r min), NSK R166 / R188ZZ pages, Emerson Bearing R2 to R24 list, checked against TFL Bearing's SKF-designation table; maker pages linked
- Page: https://xemstudio.com/objects/inch-ball-bearings-r-series-r188-r144-r166/ · JSON: https://xemstudio.com/api/geometry?object=inch-ball-bearings-r-series-r188-r144-r166 · Plain text: https://xemstudio.com/objects/inch-ball-bearings-r-series-r188-r144-r166/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); files CC BY 4.0 or their publisher's license
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**Exact dimensions.** Every file is drawn at true size with no tolerance added. The holes and pins that meet another part are listed below under Mating features, with the fit each joint needs; open those by your process's clearance before making the part.

## Notes

- R-series ball bearings are the inch-size miniature and small deep-groove bearings: R2 is 1/8 in bore, R4 is 1/4 in bore, R6 is 3/8 in, R8 is 1/2 in. R144, R166 and R188 are the thin-section sizes (1/8 x 1/4, 3/16 x 3/8 and 1/4 x 1/2 in bore x OD). R188 (6.35 x 12.7 x 3.175 open, 4.762 with shields) is a popular size for fidget spinners, small pulleys and RC parts.
- Numbers: NSK's inch-series table (R09 to R2A, the first 20 of 41 items, with r min), NSK's R166 and R188ZZ pages, Emerson Bearing's R2 to R24 list in inches (the mm there are the printed inch decimals times 25.4, and they reproduce the SKF and NSK mm values to 0.001 on every shared row), and TFL Bearing's table of the SKF catalogue designations (R1-4 to R6, WR) used as the independent mm check: NSK and TFL agree on every shared row except that NSK prints 4.762 and TFL 4.763 for 3/16 in (4.7625 mm); NSK's value is used. Two Emerson entries disagree with the other sources and are not used: its R3 bore is printed 0.1880 in (3/16 in is 0.1875; TFL / SKF 4.763 mm is shown) and its R4A OD is printed 0.6250 in, the R4 size (TFL / SKF has 19.050 mm, 3/4 in, which is shown; the R4A widths 0.2188 and 0.2812 in agree).
- R188: the open bearing is 6.35 x 12.7 x 3.175 mm (TFL, SKDIN: 0.25 x 0.5 x 0.125 in), the ZZ / 2Z / 2RS is 4.762 mm wide (NSK R188ZZ; TFL R188-2Z prints 4.763; MBA R188AZZMC3 4.762). r min 0.15 is NSK's value for the R188ZZ; NSK's R188 open page could not be read, so the open bearing has no printed r here and no file.
- Files: 22 ring envelopes for every row that NSK prints with r min (R09 to R2A, R166, R188ZZ): one solid ring, bore, OD, width and corners rounded at r min. No balls, retainer or shield. R3 to R24 and the SKF-only rows have no r read, so they are tables only.
- Left out: the other 21 NSK rows (not readable), R4A and larger r min, flanged inch bearings (FR series), thin-section 'RW' sizes, light-duty 1600 series (own page), load ratings, limiting speeds, metric miniature bearings (see the 600/MR series pages).

## Mating features (exact size; open press / slide / run / socket by your process clearance, leave designed and clamp as drawn)

| feature | exact | mates with | fit | files |
|---|---|---|---|---|
| R188ZZ shaft abutment Ø db (max) | 7.4 mm | shaft shoulder diameter must not exceed this so the inner ring face is clear (NSK R188ZZ page) | designed | R188ZZ* |
| R188ZZ housing abutment Ø Db (max) | 11.7 mm | housing shoulder diameter must not exceed this so the outer ring face is clear (NSK) | designed | R188ZZ* |
| R188ZZ fillet radius ra (max) | 0.15 mm | shaft and housing corner fillet no larger than this (NSK) | designed | R188ZZ* |

## Sizes

| designation | bore d, mm | OD D, mm | width B open, mm | width B ZZ / 2RS / 2Z, mm | bore x OD (inch, as printed) | r min, mm | source |
|---|---|---|---|---|---|---|---|
| R09 | 1.016 | 3.175 | 1.191 | — | — | 0.1 | NSK |
| R0 | 1.191 | 3.967 | 1.588 | 2.38 | — | 0.1 | NSK |
| R1 | 1.397 | 4.762 | 1.984 | 2.779 | — | 0.1 | NSK |
| R1-4 | 1.984 | 6.35 | 2.38 | 3.571 | 5/64 x 1/4 | 0.1 | NSK; TFL (SKF) |
| R133 | 2.38 | 4.762 | 1.588 | 2.38 | 3/32 x 3/16 | 0.1 | NSK; TFL (SKF) |
| R1-5 | 2.38 | 7.938 | 2.779 | 3.571 | 3/32 x 5/16 | 0.15 | NSK; TFL (SKF) |
| R144 | 3.175 | 6.35 | 2.38 | 2.779 | 1/8 x 1/4 | 0.1 | NSK; TFL (SKF) |
| R2-5 | 3.175 | 7.938 | 2.779 | 3.571 | 1/8 x 5/16 | 0.1 | NSK; TFL (SKF) |
| R2-6 | 3.175 | 9.525 | 2.779 | 3.571 | 1/8 x 3/8 | 0.15 | NSK; TFL (SKF) |
| R2 | 3.175 | 9.525 | 3.967 | 3.967 | 1/8 x 3/8 | 0.3 | NSK; TFL (SKF); Emerson |
| R2A | 3.175 | 12.7 | 4.366 | 4.366 | 1/8 x 1/2 | 0.3 | NSK; TFL (SKF); Emerson |
| R166 | 4.762 | 9.525 | 3.175 | 3.175 | 3/16 x 3/8 | 0.1 | NSK; TFL (SKF) |
| R188 | 6.35 | 12.7 | 3.175 | 4.762 | 1/4 x 1/2 | 0.15 (R188ZZ) | NSK; TFL (SKF); SKDIN, MBA |
| R155 | 3.967 | 7.938 | 2.779 | 3.175 | 5/32 x 5/16 | — | TFL (SKF) |
| R156 | 4.763 | 7.938 | 2.779 | 3.175 | 3/16 x 5/16 | — | TFL (SKF) |
| R3 | 4.763 | 12.7 | 3.967 | 4.978 | 3/16 x 1/2 | — | TFL (SKF); Emerson |
| R3A | 4.763 | 15.875 | 4.978 | 4.978 | 3/16 x 5/8 | — | TFL (SKF) |
| R168 | 6.35 | 9.525 | 3.175 | 3.175 | 1/4 x 3/8 | — | TFL (SKF) |
| R4 | 6.35 | 15.875 | 4.978 | 4.978 | 1/4 x 5/8 | — | TFL (SKF); Emerson |
| R4A | 6.35 | 19.05 | 5.558 | 7.142 | 1/4 x 3/4 | — | TFL (SKF); Emerson |
| R6 | 9.525 | 22.225 | 5.558 | 7.142 | 3/8 x 7/8 | — | TFL (SKF); Emerson |
| R8 | 12.7 | 28.575 | 6.35 | 7.938 | 0.5000 x 1.1250 x 0.2500 / 0.3125 | — | Emerson (mm = printed inch x 25.4) |
| R10 | 15.875 | 34.925 | 7.142 | 8.733 | 0.6250 x 1.375 x 0.2812 / 0.3438 | — | Emerson (mm = printed inch x 25.4) |
| R12 | 19.05 | 41.275 | 7.938 | 11.113 | 0.7500 x 1.625 x 0.3125 / 0.4375 | — | Emerson (mm = printed inch x 25.4) |
| R14 | 22.225 | 47.625 | 9.525 | 12.7 | 0.8750 x 1.875 x 0.3750 / 0.5000 | — | Emerson (mm = printed inch x 25.4) |
| R16 | 25.4 | 50.8 | 9.525 | 12.7 | 1.0000 x 2.0000 x 0.3750 / 0.5000 | — | Emerson (mm = printed inch x 25.4) |
| R18 | 28.575 | 53.975 | 9.525 | 12.7 | 1.1250 x 2.125 x 0.3750 / 0.5000 | — | Emerson (mm = printed inch x 25.4) |
| R20 | 31.75 | 57.15 | 9.525 | 12.7 | 1.2500 x 2.250 x 0.3750 / 0.5000 | — | Emerson (mm = printed inch x 25.4) |
| R22 | 34.925 | 63.5 | 11.113 | 14.288 | 1.3750 x 2.5000 x 0.4375 / 0.5625 | — | Emerson (mm = printed inch x 25.4) |
| R24 | 38.1 | 66.675 | 11.113 | 14.288 | 1.5000 x 2.6250 x 0.4375 / 0.5625 | — | Emerson (mm = printed inch x 25.4) |

## Where the files are

- NSK: [Extra small and miniature ball bearings, inch series: d, D, B, r min (first 20 of 41 items: R09 to R2A)](https://www.nsk.com/engineering/products/bearings/ball-bearings/deep-groove-ball-bearings/extra-small-ball-bearings-and-miniature-ball-bearings-inch-series.html) — web — Publisher's page; dimensions are facts
- NSK: [R166: d 4.762, D 9.525, B 3.175, r min 0.1](https://www.nsk.com/engineering/r166-esm-id.html) — web — Publisher's page; dimensions are facts
- NSK: [R144ZZ: d 3.175, D 6.35, B 2.779, r min 0.1](https://www.nsk.com/engineering/products/bearings/ball-bearings/deep-groove-ball-bearings/extra-small-ball-bearings-and-miniature-ball-bearings-inch-series/r144zz-esm-id.html) — web — Publisher's page; dimensions are facts
- NSK: [R188ZZ: d 6.35, D 12.7, B 4.762, r min 0.15; abutment db max 7.4, Db max 11.7, ra max 0.15](https://www.oss.nsk.com/r188zz-esm-id.html) — web — Publisher's page; dimensions are facts
- Emerson Bearing: [R-series miniature / instrumentation ball bearings R2 to R24: bore, OD, width (shielded / sealed and open) in inches](https://products.emersonbearing.com/printitems/miniature-instrumentation-ball-bearings/r-series-miniature-instrumentation-ball-bearings?plpver=10) — web — Publisher's page; dimensions are facts
- TFL Bearing (SKF catalogue designations): [Miniature deep groove ball bearings of the series R in inch sizes: d, D, B in mm and inches, R1-4 to R6 and WR](https://tflbearing.com/?p=5029) — web — Publisher's page; dimensions are facts
- SKDIN (distributor): [R188: 0.25 x 0.5 x 0.125 in (6.35 x 12.7 x 3.175 mm)](https://www.skdin.com/products/productid-R188) — web — Publisher's page; dimensions are facts
- MBA (miniaturebearings.com.au): [R188AZZMC3: ID 6.350, OD 12.700, width 4.762 mm](https://miniaturebearings.com.au/products/6-350x12-7x4-762-bearings-r188azzmc3) — web — Publisher's page; dimensions are facts

## Free STEP/STL (22 parts, CC BY 4.0, Xem Studio)

Index: https://xemstudio.com/files/hardware/inch-ball-bearings-r-series-r188-r144-r166/index.json

- R09-inch-miniature-ball-bearing-envelope-1.016x3.175x1.191: [STEP](https://xemstudio.com/files/hardware/inch-ball-bearings-r-series-r188-r144-r166/R09-inch-miniature-ball-bearing-envelope-1.016x3.175x1.191.step) · [STL](https://xemstudio.com/files/hardware/inch-ball-bearings-r-series-r188-r144-r166/R09-inch-miniature-ball-bearing-envelope-1.016x3.175x1.191.stl) — R09 inch-series miniature ball bearing ring envelope: bore Ø1.016, OD Ø3.175, width 1.191; one solid ring, corners rounded at r min 0.1 (NSK); no balls, retainer or shield; nominal values
- R0-inch-miniature-ball-bearing-envelope-1.191x3.967x1.588: [STEP](https://xemstudio.com/files/hardware/inch-ball-bearings-r-series-r188-r144-r166/R0-inch-miniature-ball-bearing-envelope-1.191x3.967x1.588.step) · [STL](https://xemstudio.com/files/hardware/inch-ball-bearings-r-series-r188-r144-r166/R0-inch-miniature-ball-bearing-envelope-1.191x3.967x1.588.stl) — R0 inch-series miniature ball bearing ring envelope: bore Ø1.191, OD Ø3.967, width 1.588; one solid ring, corners rounded at r min 0.1 (NSK); no balls, retainer or shield; nominal values
- R0ZZ-inch-miniature-ball-bearing-envelope-1.191x3.967x2.38: [STEP](https://xemstudio.com/files/hardware/inch-ball-bearings-r-series-r188-r144-r166/R0ZZ-inch-miniature-ball-bearing-envelope-1.191x3.967x2.38.step) · [STL](https://xemstudio.com/files/hardware/inch-ball-bearings-r-series-r188-r144-r166/R0ZZ-inch-miniature-ball-bearing-envelope-1.191x3.967x2.38.stl) — R0ZZ inch-series miniature ball bearing ring envelope: bore Ø1.191, OD Ø3.967, width 2.38; one solid ring, corners rounded at r min 0.1 (NSK); no balls, retainer or shield; nominal values
- R1-inch-miniature-ball-bearing-envelope-1.397x4.762x1.984: [STEP](https://xemstudio.com/files/hardware/inch-ball-bearings-r-series-r188-r144-r166/R1-inch-miniature-ball-bearing-envelope-1.397x4.762x1.984.step) · [STL](https://xemstudio.com/files/hardware/inch-ball-bearings-r-series-r188-r144-r166/R1-inch-miniature-ball-bearing-envelope-1.397x4.762x1.984.stl) — R1 inch-series miniature ball bearing ring envelope: bore Ø1.397, OD Ø4.762, width 1.984; one solid ring, corners rounded at r min 0.1 (NSK); no balls, retainer or shield; nominal values
- R1ZZ-inch-miniature-ball-bearing-envelope-1.397x4.762x2.779: [STEP](https://xemstudio.com/files/hardware/inch-ball-bearings-r-series-r188-r144-r166/R1ZZ-inch-miniature-ball-bearing-envelope-1.397x4.762x2.779.step) · [STL](https://xemstudio.com/files/hardware/inch-ball-bearings-r-series-r188-r144-r166/R1ZZ-inch-miniature-ball-bearing-envelope-1.397x4.762x2.779.stl) — R1ZZ inch-series miniature ball bearing ring envelope: bore Ø1.397, OD Ø4.762, width 2.779; one solid ring, corners rounded at r min 0.1 (NSK); no balls, retainer or shield; nominal values
- R1-4-inch-miniature-ball-bearing-envelope-1.984x6.35x2.38: [STEP](https://xemstudio.com/files/hardware/inch-ball-bearings-r-series-r188-r144-r166/R1-4-inch-miniature-ball-bearing-envelope-1.984x6.35x2.38.step) · [STL](https://xemstudio.com/files/hardware/inch-ball-bearings-r-series-r188-r144-r166/R1-4-inch-miniature-ball-bearing-envelope-1.984x6.35x2.38.stl) — R1-4 inch-series miniature ball bearing ring envelope: bore Ø1.984, OD Ø6.35, width 2.38; one solid ring, corners rounded at r min 0.1 (NSK); no balls, retainer or shield; nominal values
- R1-4ZZ-inch-miniature-ball-bearing-envelope-1.984x6.35x3.571: [STEP](https://xemstudio.com/files/hardware/inch-ball-bearings-r-series-r188-r144-r166/R1-4ZZ-inch-miniature-ball-bearing-envelope-1.984x6.35x3.571.step) · [STL](https://xemstudio.com/files/hardware/inch-ball-bearings-r-series-r188-r144-r166/R1-4ZZ-inch-miniature-ball-bearing-envelope-1.984x6.35x3.571.stl) — R1-4ZZ inch-series miniature ball bearing ring envelope: bore Ø1.984, OD Ø6.35, width 3.571; one solid ring, corners rounded at r min 0.1 (NSK); no balls, retainer or shield; nominal values
- R133-inch-miniature-ball-bearing-envelope-2.38x4.762x1.588: [STEP](https://xemstudio.com/files/hardware/inch-ball-bearings-r-series-r188-r144-r166/R133-inch-miniature-ball-bearing-envelope-2.38x4.762x1.588.step) · [STL](https://xemstudio.com/files/hardware/inch-ball-bearings-r-series-r188-r144-r166/R133-inch-miniature-ball-bearing-envelope-2.38x4.762x1.588.stl) — R133 inch-series miniature ball bearing ring envelope: bore Ø2.38, OD Ø4.762, width 1.588; one solid ring, corners rounded at r min 0.1 (NSK); no balls, retainer or shield; nominal values
- R133ZZS-inch-miniature-ball-bearing-envelope-2.38x4.762x2.38: [STEP](https://xemstudio.com/files/hardware/inch-ball-bearings-r-series-r188-r144-r166/R133ZZS-inch-miniature-ball-bearing-envelope-2.38x4.762x2.38.step) · [STL](https://xemstudio.com/files/hardware/inch-ball-bearings-r-series-r188-r144-r166/R133ZZS-inch-miniature-ball-bearing-envelope-2.38x4.762x2.38.stl) — R133ZZS inch-series miniature ball bearing ring envelope: bore Ø2.38, OD Ø4.762, width 2.38; one solid ring, corners rounded at r min 0.1 (NSK); no balls, retainer or shield; nominal values
- R1-5-inch-miniature-ball-bearing-envelope-2.38x7.938x2.779: [STEP](https://xemstudio.com/files/hardware/inch-ball-bearings-r-series-r188-r144-r166/R1-5-inch-miniature-ball-bearing-envelope-2.38x7.938x2.779.step) · [STL](https://xemstudio.com/files/hardware/inch-ball-bearings-r-series-r188-r144-r166/R1-5-inch-miniature-ball-bearing-envelope-2.38x7.938x2.779.stl) — R1-5 inch-series miniature ball bearing ring envelope: bore Ø2.38, OD Ø7.938, width 2.779; one solid ring, corners rounded at r min 0.15 (NSK); no balls, retainer or shield; nominal values
- R1-5ZZ-inch-miniature-ball-bearing-envelope-2.38x7.938x3.571: [STEP](https://xemstudio.com/files/hardware/inch-ball-bearings-r-series-r188-r144-r166/R1-5ZZ-inch-miniature-ball-bearing-envelope-2.38x7.938x3.571.step) · [STL](https://xemstudio.com/files/hardware/inch-ball-bearings-r-series-r188-r144-r166/R1-5ZZ-inch-miniature-ball-bearing-envelope-2.38x7.938x3.571.stl) — R1-5ZZ inch-series miniature ball bearing ring envelope: bore Ø2.38, OD Ø7.938, width 3.571; one solid ring, corners rounded at r min 0.15 (NSK); no balls, retainer or shield; nominal values
- R144-inch-miniature-ball-bearing-envelope-3.175x6.35x2.38: [STEP](https://xemstudio.com/files/hardware/inch-ball-bearings-r-series-r188-r144-r166/R144-inch-miniature-ball-bearing-envelope-3.175x6.35x2.38.step) · [STL](https://xemstudio.com/files/hardware/inch-ball-bearings-r-series-r188-r144-r166/R144-inch-miniature-ball-bearing-envelope-3.175x6.35x2.38.stl) — R144 inch-series miniature ball bearing ring envelope: bore Ø3.175, OD Ø6.35, width 2.38; one solid ring, corners rounded at r min 0.1 (NSK); no balls, retainer or shield; nominal values
- R144ZZ-inch-miniature-ball-bearing-envelope-3.175x6.35x2.779: [STEP](https://xemstudio.com/files/hardware/inch-ball-bearings-r-series-r188-r144-r166/R144ZZ-inch-miniature-ball-bearing-envelope-3.175x6.35x2.779.step) · [STL](https://xemstudio.com/files/hardware/inch-ball-bearings-r-series-r188-r144-r166/R144ZZ-inch-miniature-ball-bearing-envelope-3.175x6.35x2.779.stl) — R144ZZ inch-series miniature ball bearing ring envelope: bore Ø3.175, OD Ø6.35, width 2.779; one solid ring, corners rounded at r min 0.1 (NSK); no balls, retainer or shield; nominal values
- R2-5-inch-miniature-ball-bearing-envelope-3.175x7.938x2.779: [STEP](https://xemstudio.com/files/hardware/inch-ball-bearings-r-series-r188-r144-r166/R2-5-inch-miniature-ball-bearing-envelope-3.175x7.938x2.779.step) · [STL](https://xemstudio.com/files/hardware/inch-ball-bearings-r-series-r188-r144-r166/R2-5-inch-miniature-ball-bearing-envelope-3.175x7.938x2.779.stl) — R2-5 inch-series miniature ball bearing ring envelope: bore Ø3.175, OD Ø7.938, width 2.779; one solid ring, corners rounded at r min 0.1 (NSK); no balls, retainer or shield; nominal values
- R2-5ZZ-inch-miniature-ball-bearing-envelope-3.175x7.938x3.571: [STEP](https://xemstudio.com/files/hardware/inch-ball-bearings-r-series-r188-r144-r166/R2-5ZZ-inch-miniature-ball-bearing-envelope-3.175x7.938x3.571.step) · [STL](https://xemstudio.com/files/hardware/inch-ball-bearings-r-series-r188-r144-r166/R2-5ZZ-inch-miniature-ball-bearing-envelope-3.175x7.938x3.571.stl) — R2-5ZZ inch-series miniature ball bearing ring envelope: bore Ø3.175, OD Ø7.938, width 3.571; one solid ring, corners rounded at r min 0.1 (NSK); no balls, retainer or shield; nominal values
- R2-6-inch-miniature-ball-bearing-envelope-3.175x9.525x2.779: [STEP](https://xemstudio.com/files/hardware/inch-ball-bearings-r-series-r188-r144-r166/R2-6-inch-miniature-ball-bearing-envelope-3.175x9.525x2.779.step) · [STL](https://xemstudio.com/files/hardware/inch-ball-bearings-r-series-r188-r144-r166/R2-6-inch-miniature-ball-bearing-envelope-3.175x9.525x2.779.stl) — R2-6 inch-series miniature ball bearing ring envelope: bore Ø3.175, OD Ø9.525, width 2.779; one solid ring, corners rounded at r min 0.15 (NSK); no balls, retainer or shield; nominal values
- R2-6ZZS-inch-miniature-ball-bearing-envelope-3.175x9.525x3.571: [STEP](https://xemstudio.com/files/hardware/inch-ball-bearings-r-series-r188-r144-r166/R2-6ZZS-inch-miniature-ball-bearing-envelope-3.175x9.525x3.571.step) · [STL](https://xemstudio.com/files/hardware/inch-ball-bearings-r-series-r188-r144-r166/R2-6ZZS-inch-miniature-ball-bearing-envelope-3.175x9.525x3.571.stl) — R2-6ZZS inch-series miniature ball bearing ring envelope: bore Ø3.175, OD Ø9.525, width 3.571; one solid ring, corners rounded at r min 0.15 (NSK); no balls, retainer or shield; nominal values
- R2-inch-miniature-ball-bearing-envelope-3.175x9.525x3.967: [STEP](https://xemstudio.com/files/hardware/inch-ball-bearings-r-series-r188-r144-r166/R2-inch-miniature-ball-bearing-envelope-3.175x9.525x3.967.step) · [STL](https://xemstudio.com/files/hardware/inch-ball-bearings-r-series-r188-r144-r166/R2-inch-miniature-ball-bearing-envelope-3.175x9.525x3.967.stl) — R2 inch-series miniature ball bearing ring envelope: bore Ø3.175, OD Ø9.525, width 3.967; one solid ring, corners rounded at r min 0.3 (NSK); no balls, retainer or shield; nominal values
- R2ZZ-inch-miniature-ball-bearing-envelope-3.175x9.525x3.967: [STEP](https://xemstudio.com/files/hardware/inch-ball-bearings-r-series-r188-r144-r166/R2ZZ-inch-miniature-ball-bearing-envelope-3.175x9.525x3.967.step) · [STL](https://xemstudio.com/files/hardware/inch-ball-bearings-r-series-r188-r144-r166/R2ZZ-inch-miniature-ball-bearing-envelope-3.175x9.525x3.967.stl) — R2ZZ inch-series miniature ball bearing ring envelope: bore Ø3.175, OD Ø9.525, width 3.967; one solid ring, corners rounded at r min 0.3 (NSK); no balls, retainer or shield; nominal values
- R2A-inch-miniature-ball-bearing-envelope-3.175x12.7x4.366: [STEP](https://xemstudio.com/files/hardware/inch-ball-bearings-r-series-r188-r144-r166/R2A-inch-miniature-ball-bearing-envelope-3.175x12.7x4.366.step) · [STL](https://xemstudio.com/files/hardware/inch-ball-bearings-r-series-r188-r144-r166/R2A-inch-miniature-ball-bearing-envelope-3.175x12.7x4.366.stl) — R2A inch-series miniature ball bearing ring envelope: bore Ø3.175, OD Ø12.7, width 4.366; one solid ring, corners rounded at r min 0.3 (NSK); no balls, retainer or shield; nominal values
- R166-inch-miniature-ball-bearing-envelope-4.762x9.525x3.175: [STEP](https://xemstudio.com/files/hardware/inch-ball-bearings-r-series-r188-r144-r166/R166-inch-miniature-ball-bearing-envelope-4.762x9.525x3.175.step) · [STL](https://xemstudio.com/files/hardware/inch-ball-bearings-r-series-r188-r144-r166/R166-inch-miniature-ball-bearing-envelope-4.762x9.525x3.175.stl) — R166 inch-series miniature ball bearing ring envelope: bore Ø4.762, OD Ø9.525, width 3.175; one solid ring, corners rounded at r min 0.1 (NSK); no balls, retainer or shield; nominal values
- R188ZZ-inch-miniature-ball-bearing-envelope-6.35x12.7x4.762: [STEP](https://xemstudio.com/files/hardware/inch-ball-bearings-r-series-r188-r144-r166/R188ZZ-inch-miniature-ball-bearing-envelope-6.35x12.7x4.762.step) · [STL](https://xemstudio.com/files/hardware/inch-ball-bearings-r-series-r188-r144-r166/R188ZZ-inch-miniature-ball-bearing-envelope-6.35x12.7x4.762.stl) — R188ZZ inch-series miniature ball bearing ring envelope: bore Ø6.35, OD Ø12.7, width 4.762; one solid ring, corners rounded at r min 0.15 (NSK); no balls, retainer or shield; nominal values

## Questions

**What are the dimensions of an R188 bearing?**

Bore 1/4 in (6.35 mm), OD 1/2 in (12.7 mm), width 1/8 in (3.175 mm) open; the R188ZZ / 2Z / 2RS is 3/16 in (4.762 mm) wide.

**What are the dimensions of an R144 bearing?**

Bore 3.175 mm (1/8 in), OD 6.35 mm (1/4 in), width 2.38 mm open and 2.779 mm for R144ZZ; r min 0.1 mm.

**What are the dimensions of an R166 bearing?**

Bore 4.762 mm (3/16 in), OD 9.525 mm (3/8 in), width 3.175 mm (1/8 in); r min 0.1 mm.

**What are the dimensions of an R4 bearing?**

Bore 6.35 mm (1/4 in), OD 15.875 mm (5/8 in), width 4.978 mm (0.196 in).

**What are the dimensions of an R6 bearing?**

Bore 9.525 mm (3/8 in), OD 22.225 mm (7/8 in), width 5.558 mm open and 7.142 mm shielded.

## Fits with

- [Ball bearings, 683 to 6210 and flanged F6xx (ISO 15)](https://xemstudio.com/objects/ball-bearings-metric/)
- [Deep-groove ball bearings, series 60, 62, 63, 68 and 69: 6000 to 6310 (ISO 15)](https://xemstudio.com/objects/deep-groove-ball-bearings-series/)
- [Inch ball bearings, 1600 series (1601 to 1658): 1601, 1602, 1603, 1604, 1605, 1614, 1620, 1630 bore, OD, width (open / ZZ and 2RS)](https://xemstudio.com/objects/ball-bearings-inch-1600-series/)
- [Flanged ball bearings F6xx and MF: F623, F624, F625, F688, F695, F608 and more: bore, OD, width, flange diameter and thickness](https://xemstudio.com/objects/flanged-ball-bearings-f6xx-mf/)
- [608 ball bearing](https://xemstudio.com/objects/608-bearing/)
- [Tapered roller bearing sets, inch: LM11949 / LM11910, LM12749 / LM12710, L44649 / L44610, LM67048 / LM67010 (Timken): bore, OD, T, B, C and shoulder diameters](https://xemstudio.com/objects/tapered-roller-bearings-inch-lm11949-l44649-lm67048/)
- [Retaining rings DIN 472 (internal, for bores): ring dimensions and groove diameter d2 × width m, 8 to 110 mm](https://xemstudio.com/objects/retaining-rings-din-472-internal/)