John Guest 6mm push-fit: 6 mm OD tube, push-fit collet, metric, 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 6mm push-fit (6 mm OD)
Where 6 mm OD is used, its real dimensions, and how to connect it to other keg fittings.
Published dimensions
- Designation
- 6 mm OD
- Size / thread
- 6 mm OD tube
- Fitting form
- push-fit collet, metric
- Seals on
- single O-ring plus a stainless collet grab-ring
- Rating / role
- John Guest Speedfit metric fittings for 6mm OD tube; tube OD within 0.1mm of nominal
- Tube OD
- 6 mm
Used on: compact gas lines in the John Guest metric range, common on European kit.
6mm John Guest is a metric size and is close to but not the same as 1/4 inch (6.35mm), so a 6mm collet will not reliably hold 1/4 tube. The metric and imperial Speedfit ranges are specified separately; run one standard rather than mixing 6mm and 1/4.
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 6mm push-fit (6 mm OD)?
6 mm OD
What is the size / thread of the John Guest 6mm push-fit (6 mm OD)?
6 mm OD tube
What is the fitting form of the John Guest 6mm push-fit (6 mm OD)?
push-fit collet, metric
What is the seals on of the John Guest 6mm push-fit (6 mm OD)?
single O-ring plus a stainless collet grab-ring