Features: Extruded aluminum body for strength and light weight. Solid block vials for durability and accuracy (0.0005" /in). 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 utile surfaces for accuracy. Rare earth magnets and v-groove base for use on metal and rounded surfaces.