From The Manufacturer
Low Profile Channel Bar Set, for models MDD78/MBB78, or MDD94/MBB94, (3) channel bars 24-1/4" long x 3-1/4"W, (2) 3" diameter wheels per channel, (1) locking wheel per channel, 2-1/4" mounted height, 1/2"-13 mounting bolt thread, includes: bolts, washers, locking washers
