Anti Extrusion Back Up Rings are Manufactured from over 15 different Polymers which include. Nitrile (NBR), Fluorocarbon (Viton®), Silicon (VMQ), Fluorosilicone (FVMQ), Polyurethane, PTFE , Natural Rubber (NR), Ethylene Propylene (EPDM), Hydrogenated Nitrile Rubber (H-NBR), Carboxylated Nitrile Rubber(X-NBR), Styrene Butadiene Rubber (SBR), Perfluoroelastomer (FFKM), Chloroprene (Neoprene®).