This prologo kappa evo t20 saddle is a semi round recreational saddle with t20 rails are made from chromium giving a lightweight material that is solid enough to withstand any stress it is used in the aerospace industry to make mechanical arms so is a great compromise between mechanical resistance and strength on top of the rails is a light and strong nylon base with light pu padding which makes the kappa evo inexpensive without losing on comfort durable or weight