True Blue vials are accurate to within .0005 In. (inch) per inch in all working positions. Heavy-duty extruded aluminum frame with top read window. Three e-Band vials highlight the meniscus of the bubble to provide a clear reading at plumb and 45 Degrees, while the Dual-Pitch vial can read slope at 1/8 In. and 1/4 In. increments in either direction. Three powerful rare earth magnets for 15 Lb. (pound) of holding power. Features straight edge groove and wall grippers to allow users to extend the length of the level with any straight edge.