Powerful GripTight v-groove rare earth magnets hold to flat or round ferrous metal surfaces. Oversized solid aluminum frame is job site tough. SurroundView vials reflect ambient light for easy-read. V-groove frame fits on pipe and conduit. Oversized 1/2 In. diameter vials are easy to read. Top read windows for easy viewing. Three vials read plumb, level and 45 Degree.