Tripp Lite's 4POSTRAILKIT adjustable rackmount shelf system supports heavy UPS systems in 4 post rackmount applications. Two included pairs of expandable "L bracket" mounting rails offer front to rear support rackmount UPS systems. Pair of expandable "L brackets" adjust to any setting between 20.5 and 36 inches. Includes mounting hardware compatible with square-hole racks. Also compatible with other heavy pieces of networking or power protection equipment with 17.5 inch wide rectangular chassis.