Pro-Series 63 X 70 X 46mm V-Block & Clamp Set ~ Made of hardened tool steel that has precision machined & ground to high accuracy of the V groove. ~ Tolerance 0.005mm. ~ A versatile tool for Toolmakers & Machinists to check concentricity. ~ Clamps can easily slide in & are included. ~ Clamping range is 3-20 mm. ~ Height deviation is 0.005mm. ~ Squareness is 0.005mm.