John Guest 1/2" push-fit: 1/2" (12.7 mm) OD tube, push-fit collet, imperial, seals on single O-ring plus a stainless collet grab-ring. What it fits and the adapters to join it to other keg fittings.
Updated 05 September 2026.
John Guest 1/2" push-fit (1/2" (12.7 mm) OD)
Where 1/2" (12.7 mm) OD is used, its real dimensions, and how to connect it to other keg fittings.
Published dimensions
- Designation
- 1/2" (12.7 mm) OD
- Size / thread
- 1/2" (12.7 mm) OD tube
- Fitting form
- push-fit collet, imperial
- Seals on
- single O-ring plus a stainless collet grab-ring
- Rating / role
- John Guest Speedfit imperial fittings for 1/2 inch OD tube
- Tube OD
- 12.7 mm
Used on: larger imperial beer and water runs, kegerator trunk lines specified in inches.
1/2 inch (12.7mm) is an imperial John Guest size, close to the 12mm metric one but not the same. A 1/2 collet will not reliably grip 12mm tube and vice versa, so keep a run in one measurement standard rather than swapping between 12mm and 1/2 inch.
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
Questions and answers
What is the designation of the John Guest 1/2" push-fit (1/2" (12.7 mm) OD)?
1/2" (12.7 mm) OD
What is the size / thread of the John Guest 1/2" push-fit (1/2" (12.7 mm) OD)?
1/2" (12.7 mm) OD tube
What is the fitting form of the John Guest 1/2" push-fit (1/2" (12.7 mm) OD)?
push-fit collet, imperial
What is the seals on of the John Guest 1/2" push-fit (1/2" (12.7 mm) OD)?
single O-ring plus a stainless collet grab-ring