Constructed out of A36 steel, sides are 3/8" plate. Build to fit Class II Forks. Top Rail is 1/2" with 6 stop positions at 7", 13 1/2" and 19" each direction. The bottom rail is 3/8" bar notched for ease fork replacement. We use a solid 3/16" A36 plate with standard or custom plasma cut outs for our frame backs.