3 Vials - (1) Level, (1) Plumb, (1) 180º. Accuracy of 0.0005 in/in (0.5mm/m). Magnified Center Open Top Read Vial. 180º Rotating Vial to Duplicate Angles. Rare Earth Magnets Are Embedded into the Level For Stability and Then Milled To Provide Better Accuracy. Pipe Groove For Use on Round Surfaces.