Milton (S-715) 1/4" FNPT Female M-Style KWIK-CHANGE® Coupler Milton Industries is proud to be the creator and leader of the pneumatic industry standard M-Style coupler. This 1/4" FNPT M style brass coupler has a 1/4" basic flow size, offering a maximum of 300 PSI. Comes with Buna-N seal and air flow of 40 SCFM. You can also find this S-715 air coupler included in these Milton coupler/plug and accessory kits: No.711, No.S-210, No.S-210-14, No.S-211, No.S-212, No.S-218, No.S-220, No.S-222, No.MK506-2, No.MK1669-1, No.MK506-1, and more. Milton M-Style Kwik Change couplers are made of brass, while M-Style Kwik Change plugs are made of case-hardened steel and are plated to resist rust..