Strong holding magnetic edge allows hands free use on ferrous metal surfaces, Lifetime guarantee, Maximum accuracy, Oversized 1/2" diameter vials are easy-read, Heavy duty aluminum frame assures durability and accuracy, Ergonomic cushioned hand grips, SurroundView® vials reflect ambient light for easy-read, Top-read window maximizes readability, Field replaceable cover plates and vials, Shock absorbing end caps protect frame