Scuba O-Ring Size Finder & On-Screen Sizer

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.

Where does the o-ring go?

~~Camera~~ → No camera needed — your screen becomes the measuring tool.

1

Put a real coin ON the screen & match the circle to it

2

Lay your o-ring flat ON the screen

3

Match the blue ring to yours & identify

Screen not calibrated yet — do step 1 first.

Step 1 — Calibrate your screen

Place a coin (or any plastic card) flat on the screen and drag the slider until the outline matches it exactly.

place the object here, match the blue outline to it

Nothing is photographed or sent anywhere — the coin or card is only used as a size reference on your screen. Everything runs locally in your browser.

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.