Connect Industrial / Milton M-style air coupler to ARO 210 / A-style air coupler
How to join 1/4" Industrial (Type M) and 1/4" ARO 210 (Type A), and what stops it leaking.
Incompatible. Industrial / Milton M-style air coupler and ARO 210 / A-style air coupler do not interchange and will not seal without a matched part.
The part to buy
Industrial (Milton M-style) and ARO 210 look almost identical but do not interchange: the ARO pilot is longer and its ball groove is nearly round. A plug of one profile will push into the other coupler and either fall out or leak. Standardise your shop on one profile, or fit a coupler that is genuinely universal.
Do not judge by the 1/4 inch body alone. The two profiles share a body size and still will not lock. Buy plug and coupler as a matched interchange pair.
Related connections
Sources: Air line couplers and plugs interchange guide, ToolGuyd · Common pneumatic quick-connect interchange profiles (Milton, ARO, Euro, Orion), XHnotion · ARO 210 interchange quick coupling (Parker 50 / Hansen 210 / Tomco), fittings-adapters.com · ARO 210 Interchange Quick Couplings 50 Series, Parker