The Lowell RRD-44 is a set of mounting rails are made to fit most 23-inch wide & 44 RU high racks (LER, LFR, LSER, LGR, LSGR, LPR, LWBR and LWR rack series). These racks feature side channels to adjust rail positioning deeper into the rack, as needed. RRD rails are 11-gauge U.S. steel with a black powder epoxy finish and printed RU scale to facilitate set-up. The 1U position should be placed at the bottom of the rack for consistent loading of equipment. RRN rails accept threaded 10-32 screws. Sold in pairs