Jg12i vs JG4: specs compared
Updated 05 September 2026.
12.7 mm
Jg12i wins on tube outer diameter
On tube outer diameter, Jg12i leads: 12.7 mm versus 4 mm.
| Spec | Jg12i | JG4 |
|---|---|---|
| Designation | 1/2" (12.7 mm) OD | 4 mm OD |
| Size / thread | 1/2" (12.7 mm) OD tube | 4 mm OD tube |
| Fitting form | push-fit collet, imperial | push-fit collet, metric |
| Seals on | single O-ring plus a stainless collet grab-ring | single O-ring plus a stainless collet grab-ring |
| Rating / role | John Guest Speedfit imperial fittings for 1/2 inch OD tube | John Guest Speedfit metric fittings for 4mm OD tube; tube OD must be within 0.1mm of nominal |
| Tube OD | 12.7 mm | 4 mm |
Questions and answers
Which has the higher tube outer diameter, Jg12i or JG4?
On tube outer diameter, Jg12i leads: 12.7 mm versus 4 mm.
How do Jg12i and JG4 compare?
On tube outer diameter, Jg12i leads: 12.7 mm versus 4 mm.