RAM-style mount ball sizes: A 0.56, B 1, C 1.5, D 2.25 and E 3.38 in — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/ram-mount-ball-sizes/  (CC BY 4.0)
Basis: RAM Mounts: the letter after RAM names the ball size, A 0.56 in, B 1 in, C 1.5 in, D 2.25 in, E 3.38 in
Catalog version: 2026-10-20

Sizes: see table below
- RAM mounts join with a rubber ball on the base and a double-socket arm that clamps two balls. The letter in a RAM part number is the ball size; C-size parts carry no letter.
- Files: each ball as a sphere at the published diameter. The ball is the interface; the neck and base under it differ from part to part and are not drawn. Union a ball onto your own base to mate with a RAM arm of that size.
- Ball diameters are given in inches by RAM; the mm figures are the exact conversions. The rubber ball is drawn as a rigid sphere at its published size.

size  ball (in)  ball (mm)  used for (RAM)
A  0.56  14.224  action cameras and other very light gear
B  1  25.400  phones, GPS units, small tablets
C  1.5  38.100  large tablets, fish finders, rough rides
D  2.25  57.150  rugged tablets, laptops, heavy equipment
E  3.38  85.852  large displays, aviation and industrial use

Files elsewhere (not hosted by Xem Studio; license as stated by the publisher):
- RAM Mounts: Ball sizes by letter: A 0.56 in, B 1 in, C 1.5 in, D 2.25 in, E 3.38 in (RAM-D-202U page) — web — manufacturer page [verify license at link] — https://rammount.com/products/ram-d-202u

Free files (CC BY 4.0, Xem Studio; STEP + STL, 5 parts): https://xemstudio.com/files/hardware/ram-mount-ball-sizes/index.json
API: https://xemstudio.com/api/geometry?object=ram-mount-ball-sizes