The 685 Series Poppet Check Valve Prevents reverse flow and cross contamination and incorporates a thin elastomer disc supported by a poppet that seals on the seat. Pressure in the flow direction moves the seal off the seat first before pressure builds enough to move the poppet away from the seat. The 685 Series Check Valve maximum operating pressure of 125 psi covers a wide range of air and fluid applications. The 685 Check is a compact design with a light cracking pressure, high flow rate, and a positive seal at very low back pressure or slight vacuum. For higher cracking pressure applications, an embedded o-ring poppet is substituted for the standard elastomer disc poppet.Specification: Material Polypropylene Body & Poppet, Black. Custom order: White Seal Buna-N. Custom order: Ethylene Propylene or Fluoroelastomer (Viton®) Inlet x Outlet 1/2 Female NPT X 1/2 Female NPT1/2 Female NPT x 1/2 Male NPT1/2 Male NPT x 1/2 Female NPT1/2 Male NPT x 1/2 Male NPT Cracking Pressure 302 Stainless Spring @ 1/3 psi. Custom order: 1, 3, 7 psi or Hastelloy Spring @ 1/3, 1, 3 psi.