Item Type: Guide Post Sleeve Outer Diameter: Approx. 20mm / 0.8in Inner Diameter: Approx. 12mm / 0.5in Head Height: Approx. 18mm / 0.7in Total Height: Approx. 48mm / 1.9in Carburized Layer: Approx. 1mm / 0.04in Material: 20Cr Surface Hardness: 58-62 Concentricity: 0.005 Fit Clearance: 0.03mm 1Made of 20Cr material, which is wear?resistant and corrosion?resistant, with high toughness and strength 2Overall adopt ultra?vacuum heat treatment, bring balanced hardness of HRC58?62, not easy to wear 3The product possess high accuracy, the concentricity of a single piece is less than or equal to 0.005mm 4The column sleeve combination concentricity is less than or equal to 0.03mm, very accurate 5Guide post sleeve set come with stable structure, excellent performance and long service lifeDo not touch water, it will rust. 8 x Guide Post 8 x Guide Sleeve