Stanley 43-649 48-Inch FatMax Xtreme Magnetic Box Beam Level Durable box-beam construction is up to 5x stronger than other Stanley levels Block vials provide accuracy of 0.0005 in/in (0.5mm/m) Magnified center vial for improved visibility Machined leveling surfaces improves accuracy Rare earth magnets, which are twice as strong as basic strip magnets, are built into the level for stability