Park Tool Internal Seat Tube Clamp
Clamping directly to certain frames can cause inadvertent damage to the frame or paint finish. You need Park's Internal Seat Tube Clamp! It securely holds most bikes without clamping on any frame tube. The hex-shaped shaft resists twisting while clamped in the repair stand and it works with a huge range of seat tube sizes; anything with an inside diameter of 24mm to 32mm.