One-piece construction and made from the best materials, these R-8 collets have the edge in performance over the run-of-the-mill standards found in the market today. Total indicated runout is less than 0.00059". Made to exact specifications using carefully chosen materials, these collets and sleeves will give you accurate and durable service. Hardened to 55-60 (Rockwell C) on all clamping surfaces and 40-45 on the body spring portions, they are then precision ground to fit your fixture, socket or holder to better than industry standards.