Scuba O-Ring Size Finder
Not sure which o-ring seals your regulator, tank valve, SPG or BCD inflator? Pick your equipment below — or place your old o-ring on the screen and measure it. All sizes follow the AS568 standard used across scuba gear.
Place a coin (or any plastic card) flat on the screen and drag the slider until the outline matches it exactly.
Scuba O-Ring Size Chart — Most Common AS568 Sizes
| AS568 | ID × CS (mm) | Typical scuba use |
|---|---|---|
| -003 | 1.42 × 1.52 | SPG air spool / swivel (2 per spool) |
| -010 | 6.07 × 1.78 | LP hose to 2nd stage |
| -011 | 7.65 × 1.78 | LP port / hose 3/8" |
| -012 | 9.25 × 1.78 | HP hose / SPG port 7/16" |
| -013 | 10.82 × 1.78 | LP large port 1/2" |
| -014 | 12.42 × 1.78 | Yoke regulator / K-valve seal (the "thin" one) |
| -015 | 14.00 × 1.78 | Valve bonnet nut |
| -022 | 25.12 × 1.78 | Regulator piston ring |
| -106 | 4.42 × 2.62 | Sherwood 5121-102 |
| -107 | 5.23 × 2.62 | Sherwood 6121-129 |
| -110 | 9.19 × 2.62 | Double manifolds, spearguns |
| -111 | 10.77 × 2.62 | DIN regulators — Apeks, Atomic, Scubapro |
| -112 | 12.37 × 2.62 | Standard DIN regulator (the "thick" one) |
| -116 | 18.72 × 2.62 | Tank neck M18 (EU valves) |
| 7.5 × 1.5 | metric | BCD inflator hose quick-disconnect |
The classic mix-up: -014 (thin) and -112 (thick) share almost the same inner diameter — 12.4 vs 12.4 mm — but differ in cord thickness (1.78 vs 2.62 mm). If a brand-new yoke o-ring won't seal, you probably have the wrong one of these two. The on-screen sizer above tells them apart.
EPDM vs NBR vs Viton — Which O-Ring Material for Diving?
EPDM The all-rounder
Excellent ageing, ozone and UV resistance — outlasts standard rubber in dive gear. Great for air and recreational nitrox. Important: never use petroleum-based lubricants on EPDM — silicone grease only.
NBR The standard
Nitrile (Buna-N) is what most gear ships with. Fine for compressed air, inexpensive, but hardens and cracks with age faster than EPDM or Viton. Replace yearly.
Viton FKM For nitrox & O₂-rich mixes
The safe choice for enriched air: FKM resists oxygen degradation and heat far better than NBR/EPDM. For blends above 40% O₂ and O₂-clean equipment, Viton with oxygen-compatible grease is the standard recommendation. Planning a nitrox dive? Check your mix with our Nitrox MOD Calculator.
Fitting tips
Measure a new or clean o-ring — old rings swell with age and wrong grease, and can read half a size large. Never roll or twist a ring into its groove, use a plastic pick (metal scratches sealing surfaces), apply a thin film of silicone grease, and carry a Save-a-Dive kit — the cheapest insurance in diving.
Frequently Asked Questions
How do I find my scuba o-ring size without calipers?
Use the on-screen sizer above: hold the o-ring against your screen, drag the calibration circle to match a coin you're also holding against the screen (€1, €2 and US quarter are built in), then drag the measurement rings to match your o-ring's inner and outer edge. No camera, no photo upload — everything runs locally in your browser.
What's the difference between AS568-014 and AS568-112?
They're the classic mix-up: both have almost the same inner diameter (~12.4mm) but different cross-section thickness — -014 is 1.78mm (thin, used on yoke/K-valve regulator seals) and -112 is 2.62mm (thick, used on DIN regulators). If a brand-new yoke o-ring won't seal, you likely have a -112 instead of a -014, or vice versa. The sizer distinguishes them by thickness, not just diameter.
Can I use a coin to measure an o-ring?
Yes. Coins are manufactured to precise, fixed diameters, so they work as a free calibration reference. Our sizer supports €1, €2 and US quarter — pick whichever you have, place it in the calibration zone, and the tool scales the measurement grid to match.
What material o-ring should I use for diving — EPDM, NBR or Viton?
EPDM is the best all-rounder for air and recreational nitrox (excellent ageing/ozone/UV resistance — use only silicone grease, never petroleum-based). NBR (Buna-N) is the cheaper factory-standard, fine for air but hardens faster — replace yearly. Viton (FKM) is the safe choice above 40% O₂ and for O₂-clean equipment, since it resists oxygen degradation and heat far better than the other two.
How often should I replace scuba o-rings?
Replace whenever you open a sealed compartment (battery change, regulator service) — it's cheap insurance against a flood. Even without opening anything, NBR o-rings are best replaced yearly since they harden with age; EPDM and Viton last longer but should still be checked each service for swelling, flat spots or cracking.