The Wellington Arena features a set-in design that is user friendly for set up. The rails are pre-measured so you simply place the rail into the supports which assures perfect measurements every time. The Wellington supports are made with UV stabilized polyethylene. The 100% UV treated material is super tough and durable and will withstand abuse and all weather conditions. The Wellington Arenas are highly stable in high wind areas. The rails are 1 1/2"x 5 1/2" ribbed rails that are made of 100% UV resistant PVC. Ribbed rails add strength. Durability and eliminates sagging. The Wellington Arena sets the rail height at the 12" required rail height. The support cones are also sold separately and designed to house round rails. If you choose you can set up your arena using fence rails or jump rails you have on hand. This unique design offers advantages not found with other arenas.