FFL vs Post Firestone: specs compared
Updated 05 September 2026.
5
specs differ
FFL and Post Firestone differ on 5 specs: designation, size / thread, fitting form, seals on, rating / role.
| Spec | FFL | Post Firestone |
|---|---|---|
| Designation | 1/4" FFL (7/16"-20 UNF) | 9/16"-18 UNF |
| Size / thread | 7/16"-20 UNF female thread, 45 degree flare seat | 9/16"-18 UNF (about 14.3 mm major) |
| Fitting form | SAE 45 degree flare, female | UNF male post thread |
| Seals on | mates against a male 45 degree flare face | poppet inside the post; post base O-ring seals to the keg lid |
| Rating / role | the female half of the homebrew flare standard | gas and liquid posts share the thread; disconnect snaps over the outside |
Questions and answers
How do FFL and Post Firestone compare?
FFL and Post Firestone differ on 5 specs: designation, size / thread, fitting form, seals on, rating / role.