... ,Fsil,VITON(FKM)&Dow elastomers,Neoprene,HNBR,Natural rubber,SBR,IR,IIR(butyl rubber),ACM ect.NSF an KTW approved for material ... .Have advanced CNC machine and technique to cut bonding washer molds by ourself.7)Hardness is between 30and 90 Shore-A ... resistance, anti-ozone and aging, wearable,great flexibility etc. various rubber products