Stanley 43-679 78-Inch FatMax Xtreme 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 Limited Lifetime Warranty 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 Limited Lifetime Warranty