Ball-lock quick disconnect (ball-lock QD, MFL or barb tail)
Where ball-lock QD, MFL or barb tail is used, its real dimensions, and how to connect it to other keg fittings.
Published dimensions
- Designation
- ball-lock QD, MFL or barb tail
- Size / thread
- snaps over the corny post; tail is 1/4" MFL (7/16-20 UNF) or a 1/4"/5/16" barb
- Fitting form
- snap-on quick disconnect
- Seals on
- O-ring seals over the post shoulder; the tail seals by flare or clamp
- Rating / role
- the universal ball-lock keg connector; gas and liquid are keyed differently
Used on: ball-lock corny kegs (Cornelius, Firestone, Spartanburg); grey or white for gas, black for liquid.
The disconnect snaps over the post, it does not thread onto it, so the post thread never touches your line. The tail is where you choose: an MFL flare tail needs an FFL or barb swivel, a barb tail takes vinyl line under a clamp. Gas and liquid bodies are keyed so they only fit their own post.
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
Sources: Keg Outlet corny keg disconnects (ball lock and pin lock, MFL/barb tails) ยท DraftMag ball lock vs pin lock disconnect comparison