These swing seats are made from EPDM: Ethylene-propylene-diene-monomer which is a synthetic rubber material which helps prevent crazing, cracking and oxidizing. They measure 5" x 24" and have 2 stainless steel inserts at either end of the seat with a stainless steel strip spot welded to each of end inserts. There are 4 stainless steel washers, 1/2" thick, welded to each side of each insert then molded into the rubber. The seat should last 2 years in harsh conditions and up to 5 years in optimal conditions. Some conditions may require replacement sooner. Holds up to 1400 lbs.