Sanke G coupler (Grundy) (type G vs SodaStream CO2 cylinder (TR21-4 (often pin-valve)): specs compared
Updated 05 September 2026.
5
specs differ
Sanke G coupler (Grundy) (type G and SodaStream CO2 cylinder (TR21-4 (often pin-valve)) differ on 5 specs: designation, size / thread, fitting form, seals on, rating / role.
| Spec | Sanke G coupler (Grundy) (type G | SodaStream CO2 cylinder (TR21-4 (often pin-valve)) |
|---|---|---|
| Designation | type G, Grundy | TR21-4 (often pin-valve) |
| Size / thread | 5/8" BSP beer and gas ports, Grundy probe | TR21 x 4 mm trapezoidal, frequently behind a proprietary quick-connect valve |
| Fitting form | single-probe keg coupler | soda-maker CO2 cylinder |
| Seals on | flat washer on each threaded port | O-ring on the valve stem |
| Rating / role | the British Grundy standard | small refillable soda cylinder brewers repurpose for kegging |
Questions and answers
How do Sanke G coupler (Grundy) (type G and SodaStream CO2 cylinder (TR21-4 (often pin-valve)) compare?
Sanke G coupler (Grundy) (type G and SodaStream CO2 cylinder (TR21-4 (often pin-valve)) differ on 5 specs: designation, size / thread, fitting form, seals on, rating / role.