Package Included: 12PCS Collets (3/32"", 1/8"", 3/16"", 1/4"", 5/16"", 3/8"", 7/16"", 1/2"", 9/16"", 5/8"", 11/16"" and 3/4""), 1 PCS R8 Shank Threading (7/16''-20), and 1 PCS Wrench. Function: Specially designed for milling, drilling, CNC, tapping, lathe and other clamping tool. Accuracy and Run-out Tolerance are up to 0.0004"". Installation Instructions: First, tilt the collet and place it on the nut of the holder sleeve, then tighten the nut. High-Quality : Adopt high-quality 65MN high-quality spring steel elastic design, high elasticity, large clamping force, not easy to deform after repeated use. NOTE: If you install the collet correctly, you will find that the working position of the collet is in the center of the holder.