Precision machine hardened and ground concentric. Made of high quality tool steel. Tool Holder Bushing for universal use on CNC turning machines to adapt a wide variety of boring bars, drills, reamers and shank type tools. Hardened and precision ground to highest concentricity. Measurements are posted in the pictures. Please feel free to reach out with any questions you may have. I will do my best to answer your questions and can provide more pictures if need be. Priced low to sell fast. I have so much that I can’t keep up with posting it. Thank you for your interest and support.