Industrial / Milton M-style air coupler (1/4" Industrial (Type M))

Used on: the default air-tool coupler in the US and much of the UK, on most home and light-commercial compressors.

The Industrial or Milton M-style is the most common 1/4 inch air coupler. A V-style high-flow coupler will accept an M-style plug, but an ARO or Automotive coupler will not, so a plug and coupler from the same interchange are the only reliable pairing.

Quick-connect click fittings from Hozelock, Gardena and Karcher are proprietary and do not interchange. They all sit on top of a standard thread underneath, so the reliable way to move between brands is to adapt at the threaded tap or hose-end fitting, then use each brand's own connector above it.