The Thomson seat clamp features a patented design. A pivoting cylindrical nut helps provide the most direct and efficient application of clamping force. This design gives more even and stronger clamping force versus other designs so it can help to eliminate slipping seatposts. The Thomson seat clamp is CNC machined and has the extreme high-quality expected from Thomson products. Measure the outside diameter of the seat tube extension of the frame to determine correct size.