The Pinarello Bolide TT, TR, and TR+ framesets utilize a rear pressure wedge system for securing the aero carbon seatpost. Should you lose or damage your wedge, this is the replacement part you need to keep your post in place without damaging it. The wedge is perfectly shaped to slide into the frame space behind the seatpost, and accepts pressure from the two rear facing bolts to secure. There is no other part you should utilize, as this is the only Pinarello part made and the only part that maintains your frame warranty. Fasten only to recommended torque specification.