It is 2~4mm larger than the workpiece when opened, and it is best to be as big as the outer diameter of the workpiece when clamped. The best way is to clamp a small workpiece in the middle of the sleeve and then turn the steps outside the sleeve to the same size as the outer diameter of the workpiece, and then just hold the small workpiece to clamp the workpiece to be turned. When the difference between the inner diameter of the sleeve and the outer diameter of the workpiece is too large, the workpiece is easy to deform, which is also commonly known as the clamping triangle!