This seat bag is designed to fit most railed seats, with leather straps that wrap securely around the seat and an additional strap around the seat post for extra stability. The top flap covers the bag completely, with rain flaps for added protection against the elements. Need a size reference? It comfortably holds a 4-pack of 12oz cans. Oh! And it also has a slip pocket on the inside and a plastic plate in the back to help keep its shape.