http://http://orthoseat.com/folding-chair-portable-folding-seat/

I just discovered the OrthoSeat, a portable chair that has been a familiar sight at sports events since 1989! It's crafted of rubber tree wood slats (lightest of the hardwoods) and durable 100% cotton canvas. The Orthoseat portable chair supports the back properly— which allows you to sit for extensive\long periods of time without back problems. I can see why this portable folding seat has enjoyed such widespread approval over such a short time. It's terrific!