These are universal extensions for a variety of uses. Most common is to extend the width of the frame to mount leaf spring hangers and shackle mounts further outboard for wider axle housing mounts (such as installing full-width axles in a narrow vehicle). The platforms can also be used as a coil spring mount, motor mount frame platform, and a number of other uses. This is the strongest mounting platform we offer. 1/4" steel plate, brake bent with gusset for strength