This is one of the heaviest duty residential swing seats on the market. This seat is 5" wide x 24" long. There are two stainless steel inserts with a stainless strip welded to connect the inserts. These inserts have four stainless steel washers welded to them. This is then enclosed in EPDM rubber. Therefore, washers are not visible from the outside of the swing seat. EPDM: Ethylene-propylene-diene-monomer is a synthetic rubber material which helps prevent crazing, cracking and oxidizing. Natural rubber is often made from recycled tires etc, and you are never sure what the actual rubber mixture is. It often wears off on children’s clothes. It cracks and crazes, making the seat unsightly and allowing moisture to get into the seat. This makes the seat deteriorate at a much quicker rate. Our seats are made of EPDM rubber that is made especially for our swing seats. The rubber does not rub off on children’s clothes and the seats last much longer than natural rubber swings. Unlike seats made of polymer, seats made of EPDM rubber hold up well in extreme temperatures, both very hot and very cold.