Brass Double Check Valve containg 2 x OV20 Cartridges, supplied with a DN20 Brass Spigot Adapter, DN20 Brass Shortened Socket Fitting and a 25 x 2.5 mm Nitrile O-ring. For use with the SPED20 and SPWP20 Standpipe Assemblies. The Low Loss Double Check Valve provides Fluid Category 3 protection and affords a good flow of water even in low pressure areas by virtue of high-flow cartridges.