... 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, NBR + PVC, natural rubber, SBR, IR, IIR ... (butyl rubber), CR (neoprene), SBR, AU, ACM, CO, etc. ...