PRIMA plain bearing chucks are widely used for hand operated percussion drilling machines - smaller and intermediate sizes. Rohm's industrial quality chuck has fully hardened and ground working components which offer exceptionally high accuracy, gripping power and durability. PRIMA plain bearing 10mm Keyed Drill Chucks, with female mount, are widely used for hand operated percussion drilling machines - smaller and intermediate sizes. This industrial quality chuck has fully hardened and ground working components which offer exceptionally high accuracy, gripping power and durability. Specifications:Size: 1/2 x 20.