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Sanke M coupler (type M)

Where type M is used, its real dimensions, and how to connect it to other keg fittings.

Published dimensions

Designation
type M
Size / thread
5/8" BSP beer and gas ports, M-system probe
Fitting form
single-probe keg coupler
Seals on
flat washer on each threaded port
Rating / role
the M-system standard

Used on: certain German kegs and some Pilsner Urquell kegs (confirm by keg).

The M coupler is one of the less common heads, close to the S system but with its own probe and not interchangeable with it. Its dispense ports are 5/8 BSP like the rest, so only the head choice is unusual, the line connection is standard.

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.

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Sources: Iron Mountain Refrigeration keg coupler guide (D, S, A, G, M, U Sankey systems) ยท HowdyBrewer / Micro Matic keg couplers (D, S, A, G, M, U systems)