True Blue vials are accurate to within 0.0005 In. (inch) per inch in all working positions. Vials display angles of 0, 30, 45 and 90 Degree. V-groove for pipe and conduit work. Powerful neodymium magnets for superior holding strength. Anodized aluminum frame. No. EM71.8: Length: 8 In., Material: Aluminum, Magnetic: Yes, Number of Vials: 4, Pkg Qty: 1, Package Type: Clamshell