... ring are made of various materials,such as Silicone O-ring,NBR O-ring,HNBR O-ring,EPDM O-ring,CR O-ring,FPM O-ring ... ,PU O-ring.Different material ... O-rings have different uses.The nbr O-ring can be wanter-proof,oil-proof,abrasion proof ... size is 670*7.We also produce as customer request.Welcome to your Enquiry! high wearable NBR O-ring ...