Features: High precision: +/-20 seconds, 0.0001 inches per inch. Each angle block has 4 holes for easy installation. Made of precision-ground hardened steel, the angle blocks can offer precision measurement and long-term use. Including 1 × 30-60-90 degree angle block, 1 × 45-45-90 degree angle block and one matching case, easy to carry. Angle blocks can be used to calibrate and measure an exact angle. Specifications:Material: Steel Measuring Range: 30-45-60-90°Note:Please allow 1-3cm error due to manual measurement. Pls make sure you don't mind before you bid. Due to the difference between different monitors, the picture may not reflect the actual color of the item. Package Included:2x Angle Block Set1x Case