Extruded aluminum body for strength and light weight. 3 solid block vials for durability and accuracy (0.0005"). Rotating vial for identifying and duplicating angles, slopes, and pitch. Magnified center vial for readability. Over-molded rubber end caps for shock-resistance. Top and bottom milled surfaces for accuracy. Rare Earth magnets and v-groove base for use on metal and rounded surfaces. Length: 9".