EVABarrier 4mm ID x 8mm OD line: 4 mm inner diameter, 8 mm outer diameter double-wall EVA line, double-wall EVA beer / gas tubing, seals on the 8mm OD is what a Duotight 8mm or John Guest 5/16 collet grips. What it fits and the adapters to join it to other keg fittings.
Updated 05 September 2026.
EVABarrier 4mm ID x 8mm OD line (4 mm ID / 8 mm OD)
Where 4 mm ID / 8 mm OD is used, its real dimensions, and how to connect it to other keg fittings.
Published dimensions
- Designation
- 4 mm ID / 8 mm OD
- Size / thread
- 4 mm inner diameter, 8 mm outer diameter double-wall EVA line
- Fitting form
- double-wall EVA beer / gas tubing
- Seals on
- the 8mm OD is what a Duotight 8mm or John Guest 5/16 collet grips
- Rating / role
- low gas permeability line matched to the 8mm push-in size; fitting rated to 100 psi, tube burst well above
- Tube OD
- 8 mm
Used on: gas lines and short beer runs on the 8mm Duotight system, where a narrow 4mm bore suits a gas jumper.
This line is sized by two numbers: the 4mm inner bore and the 8mm outer wall. The 8mm OD is what the fitting grips, so it takes an 8mm Duotight or 5/16 John Guest collet. The narrow 4mm bore adds pour resistance, which is why it is favoured for gas rather than long beer runs.
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 EVABarrier 4mm ID x 8mm OD line (4 mm ID / 8 mm OD)?
4 mm ID / 8 mm OD
What is the size / thread of the EVABarrier 4mm ID x 8mm OD line (4 mm ID / 8 mm OD)?
4 mm inner diameter, 8 mm outer diameter double-wall EVA line
What is the fitting form of the EVABarrier 4mm ID x 8mm OD line (4 mm ID / 8 mm OD)?
double-wall EVA beer / gas tubing
What is the seals on of the EVABarrier 4mm ID x 8mm OD line (4 mm ID / 8 mm OD)?
the 8mm OD is what a Duotight 8mm or John Guest 5/16 collet grips