At 150mm diameter these jaws allow you to reverse chuck smaller workpieces without having to use large diameter wood jaw plates. The conical rubber buttons pull your work gently and securely back against jaw plates without damaging its edge. You can use them externally or internally (120mm). A series of tapped holes offers you a variety of diameters. The jaws come with rubber buttons. They will fit either 80mm or 100mm chucks.As an alternative to using the buttons, stacking turn studs are available as an optional extra. These are designed as a primary holding device for all manner of round or square blanks and, giving a very secure holding method, they can be used singly or doubled up using the longer bolts supplied.