The 48 in. Magnetic I-Beam level offers precision leveling accuracy in a robust and durable design. It features durable block vials. instead of standard vials. that provide leveling accuracies of /- 0.0005 in. and enhanced damage resistance. Each base is designed with V-Grooves for accurate reading on both flat and rounded surfaces. and each end cap is constructed with over-molding for enhanced impact protection. Rare earth magnets deliver superior holding strength.