Miniature plastic check valves, Our housing can be molded of Nylon, Polypropylene, PVDF, Acetal, or Polycarbonate, or Acrylic. Diaphragms are made from Fluorosilicone, Viton®, Epdm, Kalrez®, Silicone: FDA and USP Class VI. Plastic valves are barbed for 1/8, 3/16, 1/4, 5/16 and 3/8 ID tubing. Threads of 10-32, 1/4-28 and pipe sizes of 1/8 NPT.