DIN 477 No.6 CO2 valve (W21.8): W21.8 x 1/14" (21.8 mm, 14 TPI) right hand, external, cylinder valve outlet nut, external, seals on captive O-ring or washer in the nut against the valve outlet. What it fits and the adapters to join it to other keg fittings.

Updated 05 September 2026.

Bench / Fittings / Fitting

DIN 477 No.6 CO2 valve (W21.8) (W21.8 x 1/14" RH)

Where W21.8 x 1/14" RH is used, its real dimensions, and how to connect it to other keg fittings.

Published dimensions

Designation: W21.8 x 1/14" RH
Size / thread: W21.8 x 1/14" (21.8 mm, 14 TPI) right hand, external
Fitting form: cylinder valve outlet nut, external
Seals on: captive O-ring or washer in the nut against the valve outlet
Rating / role: the German DIN 477 designation for the European CO2 outlet, the same physical thread as W21.8 and BS 341 No.8

Used on: European CO2 cylinders labelled by their DIN 477 number rather than W21.8.

DIN 477 No.6, W21.8 and BS 341 No.8 all name the same 21.8mm x 14 TPI right-hand CO2 outlet, so a regulator sold for any one of those labels fits the others. The confusion is only in the naming, not the thread; confirm the number on your cylinder, then buy the matching W21.8 regulator.

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 W21.8 CO2 cylinder valve to DIN 477 No.6 CO2 valve (W21.8)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 DIN 477 No.6 CO2 valve (W21.8) (W21.8 x 1/14" RH)?

W21.8 x 1/14" RH

What is the size / thread of the DIN 477 No.6 CO2 valve (W21.8) (W21.8 x 1/14" RH)?

W21.8 x 1/14" (21.8 mm, 14 TPI) right hand, external

What is the fitting form of the DIN 477 No.6 CO2 valve (W21.8) (W21.8 x 1/14" RH)?

cylinder valve outlet nut, external

What is the seals on of the DIN 477 No.6 CO2 valve (W21.8) (W21.8 x 1/14" RH)?

captive O-ring or washer in the nut against the valve outlet