CGA-320 (flat seat detail): 0.825"-14 NGO right hand, external, flat-seat nipple, cylinder valve outlet nut, flat seat, seals on flat nylon or fibre washer inside the nut against the flat valve seat. What it fits and the adapters to join it to other keg fittings.

Updated 05 September 2026.

Bench / Fittings / Fitting

CGA-320 (flat seat detail) (0.825"-14 NGO RH, flat nipple)

Where 0.825"-14 NGO RH, flat nipple is used, its real dimensions, and how to connect it to other keg fittings.

Published dimensions

Designation: 0.825"-14 NGO RH, flat nipple
Size / thread: 0.825"-14 NGO right hand, external, flat-seat nipple
Fitting form: cylinder valve outlet nut, flat seat
Seals on: flat nylon or fibre washer inside the nut against the flat valve seat
Rating / role: the CO2-only cylinder connection on North American refillable tanks

Used on: carbon dioxide cylinders; the flat seat is what distinguishes it from the conical CGA-300 and round CGA-326.

CGA-320 is a flat-seat nipple, so it needs its flat washer to seal and a conical CGA-300 valve will not seat against a flat CGA-320 nut. The flat seat is the detail that keeps CO2 (320) apart from nitrous oxide (326) and ethyl chloride (300) which share the 0.825-14 thread but differ in seat shape.

Flare fittings seal on the 45 degree flare face and must never be taped. Push-in fittings seal on an O-ring against the tube wall and need the tube cut square. Barbs seal under a worm clamp. Getting the sealing method right matters more than the thread label, because most homebrew leaks are a taped flare or an unclamped barb.

Connect this fitting

Connect CGA-320 CO2 cylinder valve to CGA-320 (flat seat detail)direct fit CGA-320 CO2 cylinder valverelated fitting (0.825"-14 NGO RH)W21.8 CO2 cylinder valverelated fitting (W21.8-14 (DIN 477 / BS 341 No.8))G5/8 regulator inletrelated fitting (G5/8 (BSP parallel))TR21-4 soda cylinder valverelated fitting (TR21x4 (soda / SodaStream-style))CGA-580 nitrogen / beer-gas cylinder valverelated fitting (0.965"-14 NGO RH)SodaStream CO2 cylinderrelated fitting (TR21-4 (often pin-valve))

Questions and answers

What is the designation of the CGA-320 (flat seat detail) (0.825"-14 NGO RH, flat nipple)?

0.825"-14 NGO RH, flat nipple

What is the size / thread of the CGA-320 (flat seat detail) (0.825"-14 NGO RH, flat nipple)?

0.825"-14 NGO right hand, external, flat-seat nipple

What is the fitting form of the CGA-320 (flat seat detail) (0.825"-14 NGO RH, flat nipple)?

cylinder valve outlet nut, flat seat

What is the seals on of the CGA-320 (flat seat detail) (0.825"-14 NGO RH, flat nipple)?

flat nylon or fibre washer inside the nut against the flat valve seat