Factor Ostro Nylon Seatpost RedThis replacement seat shim is specifically designed for use on the Factor Ostro Vam bike. This kit consists of the wedge and everything required to hold the saddle in place. Quick and easy installation. Factor Ostro Nylon Seatpost RedThis replacement seat shim is specifically designed for use on the Factor Ostro Vam bike. This kit consists of the wedge and everything required to hold the saddle in place. Quick and easy installation.