Features: 1) We can supply 25#, 30#, 35# and 40# silicone valve core seals 2) High quality Features:1) Available material: ... materials for silicone, NBR, fluorosilicone,viton (FKM), viton DuPont & Dow elastomers, neoprene, HNBR ... are accepted 7) Available in various sizes and colors Rubber silicone valve core