Johnson 24" Magnetic Heavy Duty Aluminum I-Beam Level. It has a strong holding magnetic edge that allows hands-free use on ferrous metal surfaces. The oversized 1/2" diameter vials are easy to read. The job site tough, ergonomic cushioned hand grips provide a comfortable grip. The surround view vials reflect ambient light for easy reading. The top read window maximizes readability. The durable protective, field replaceable, acrylic cover plates protect vials from water and dust. The shock absorbing end caps protect the frame when dropped. It has a lifetime accuracy warranty.