True Blue vials are accurate to within 0.00005in. per inch in all 10 level and plumb working positions. Super-strong anodized I-beam frame with shock-absorbing end plates. Solid block acrylic vials wont break, leak or fog. Top-read window. Limited lifetime warranty. U.S.A. Material: Anodized I-beam, Length (in.): 24, Application: General