1/4" Series Lincoln Long Nose Type "A". Plated steel couplers have hardened steel balls and stainless steel springs. Coupler plugs are heat treated to reduce wear on critical mating surfaces. The Lincoln Series of plugs are easily identified by the long plug end. The couplers are identified with one narrow and one wide groove on the sleeve. Couplers interchange with Lincoln as well as units produced by other manufacturers. Maximum working pressure 300 PSI.