Jg38 vs JG4: specs compared
Updated 05 September 2026.
9.53 mm
Jg38 wins on tube outer diameter
On tube outer diameter, Jg38 leads: 9.53 mm versus 4 mm.
| Spec | Jg38 | JG4 |
|---|---|---|
| Designation | 3/8" (9.5 mm) OD | 4 mm OD |
| Size / thread | 3/8" (9.53 mm) | 4 mm OD tube |
| Fitting form | push-fit collet, imperial | push-fit collet, metric |
| Seals on | single O-ring plus stainless collet grab-ring | single O-ring plus a stainless collet grab-ring |
| Rating / role | Speedfit acetal fittings rated to 12 bar at 20 C, 6 bar at 65 C | John Guest Speedfit metric fittings for 4mm OD tube; tube OD must be within 0.1mm of nominal |
| Tube OD | 9.53 mm | 4 mm |
Questions and answers
Which has the higher tube outer diameter, Jg38 or JG4?
On tube outer diameter, Jg38 leads: 9.53 mm versus 4 mm.
How do Jg38 and JG4 compare?
On tube outer diameter, Jg38 leads: 9.53 mm versus 4 mm.