Amazon.com: SMC KV2H11-35S DOT brass fitting, male connector, KV2 FITTING, Straight Threaded-to-Tube Adapter, NPT 1/4" Male, Push In 3/8" - package of 10 : Industrial & Scientific
SMC KFH08N-02 Brass Insert Tube Fitting, Connector, 8 mm Tube OD x 6 mm Tube ID x 1/4" BSPT Male: Push To Connect Tube Fittings: Amazon.com: Industrial & Scientific
SMC KQ2R04-06A connectors - kq2 fitting family kq2 4mm - fitting, plug-in reducer - package of 10: Industrial Air Cylinder Accessories: Amazon.com: Industrial & Scientific
SMC KQH16-04S Male Connector/Straight Union, Blue Release, Series KQ2, RC 1/2 Port Size, ONE-Touch Fitting, 16 MM OD, with Thread SEALANT, Black Body: Amazon.com: Industrial & Scientific