# Plastic syringes 1–60 mL as pistons and cylinders

> What is the inside diameter of a 10 mL syringe?

- Category: Hardware › Found & household materials
- Kind: Standard part
- Basis: Typical BD / Terumo Luer-slip barrel dimensions; ID is what sets the stroke volume (±0.3 mm between brands: measure yours)
- Page: https://xemstudio.com/objects/plastic-syringes/ · JSON: https://xemstudio.com/api/geometry?object=plastic-syringes · Plain text: https://xemstudio.com/objects/plastic-syringes/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); linked files under their publishers' licenses

## Notes

- Barrel ID (and OD): 1 mL 4.7 (6.5), 3 mL 8.6 (10.0), 5 mL 12.0 (13.6), 10 mL 14.5 (15.9), 20 mL 19.1 (21.0), 30 mL 21.7 (23.6), 60 mL 26.7 (29.0) mm. Stroke volume per mm: ID²×π/4, so a 10 mL moves 0.165 mL per mm.
- As a Stirling power piston: pull the rubber plunger tip, use the bare plunger as a near-frictionless piston (0.1 mm clearance) or keep the tip for a sealed, higher-friction piston. Glass syringes are the premium version: 10 mL glass is Ø15.0 ID, nearly zero friction.
- Polypropylene softens at 100 °C: the syringe is always the cold-side power cylinder, 50 mm or more from the flame. The Luer tip is a convenient 4.2 mm pressure port.

## Sizes

| syringe | barrel_id_mm | barrel_od_mm | length_mm | ml_per_mm_stroke |
|---|---|---|---|---|
| 1ml | 4.7 | 6.5 | 57 | 0.017 |
| 3ml | 8.6 | 10.0 | 70 | 0.058 |
| 5ml | 12.0 | 13.6 | 76 | 0.113 |
| 10ml | 14.5 | 15.9 | 90 | 0.165 |
| 20ml | 19.1 | 21.0 | 103 | 0.287 |
| 30ml | 21.7 | 23.6 | 105 | 0.37 |
| 60ml | 26.7 | 29.0 | 125 | 0.56 |

## Where the files are

- Wikipedia: [Syringe](https://en.wikipedia.org/wiki/Syringe) — web — CC BY-SA 4.0 (text)
- BD: [BD syringe specifications](https://www.bd.com/en-us/products-and-solutions/products/product-families/bd-luer-lok-syringes) — web — BD site (verify at link)
- Long Earth Society: [Engine builds (videos and write-ups)](https://longearthsociety.com/engineering/) — web, video — LES site

## Free STEP/STL (7 parts, CC BY 4.0, Xem Studio)

Index: https://xemstudio.com/files/hardware/plastic-syringes/index.json

- syringe-1ml: [STEP](https://xemstudio.com/files/hardware/plastic-syringes/syringe-1ml.step) · [STL](https://xemstudio.com/files/hardware/plastic-syringes/syringe-1ml.stl) — 1ml Luer-slip syringe: barrel ID 4.7, OD 6.5, 57 mm long; plunger shown mid-stroke
- syringe-3ml: [STEP](https://xemstudio.com/files/hardware/plastic-syringes/syringe-3ml.step) · [STL](https://xemstudio.com/files/hardware/plastic-syringes/syringe-3ml.stl) — 3ml Luer-slip syringe: barrel ID 8.6, OD 10.0, 70 mm long; plunger shown mid-stroke
- syringe-5ml: [STEP](https://xemstudio.com/files/hardware/plastic-syringes/syringe-5ml.step) · [STL](https://xemstudio.com/files/hardware/plastic-syringes/syringe-5ml.stl) — 5ml Luer-slip syringe: barrel ID 12.0, OD 13.6, 76 mm long; plunger shown mid-stroke
- syringe-10ml: [STEP](https://xemstudio.com/files/hardware/plastic-syringes/syringe-10ml.step) · [STL](https://xemstudio.com/files/hardware/plastic-syringes/syringe-10ml.stl) — 10ml Luer-slip syringe: barrel ID 14.5, OD 15.9, 90 mm long; plunger shown mid-stroke
- syringe-20ml: [STEP](https://xemstudio.com/files/hardware/plastic-syringes/syringe-20ml.step) · [STL](https://xemstudio.com/files/hardware/plastic-syringes/syringe-20ml.stl) — 20ml Luer-slip syringe: barrel ID 19.1, OD 21.0, 103 mm long; plunger shown mid-stroke
- syringe-30ml: [STEP](https://xemstudio.com/files/hardware/plastic-syringes/syringe-30ml.step) · [STL](https://xemstudio.com/files/hardware/plastic-syringes/syringe-30ml.stl) — 30ml Luer-slip syringe: barrel ID 21.7, OD 23.6, 105 mm long; plunger shown mid-stroke
- syringe-60ml: [STEP](https://xemstudio.com/files/hardware/plastic-syringes/syringe-60ml.step) · [STL](https://xemstudio.com/files/hardware/plastic-syringes/syringe-60ml.stl) — 60ml Luer-slip syringe: barrel ID 26.7, OD 29.0, 125 mm long; plunger shown mid-stroke

## Questions

**What is the inside diameter of a 10 mL syringe?**

About 14.5 mm (OD 15.9); a 20 mL is 19.1 mm, a 60 mL 26.7 mm. Brands vary by ±0.3 mm.

**How do I use a syringe as a Stirling engine piston?**

Cut the barrel to length, keep it on the cold side, and run the plunger without its rubber tip for low friction (or with it for a seal). The 10 mL size matches a 12 oz can displacer well.

**How much volume does a syringe move per mm?**

ID² × π / 4: 10 mL (14.5 mm) → 0.165 mL/mm; 20 mL (19.1 mm) → 0.287 mL/mm; 60 mL (26.7 mm) → 0.56 mL/mm.

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