True Blue vials are accurate to within 0.0005 In. (inch) per inch in all working positions. Heavy-duty 12 In. extruded aluminum frame. 4 vials read plumb, level, 45 Degree, and Vari-Pitch. Vari-Pitch vial reads slope in 1/8 In. increments. Powerful, full-length magnetic edge. 12m metric pitch.