TRIPP LITE's 4POSTRAILKITHD is an adjustable rackmount shelf system that supports heavy UPS systems in four-post rack mount applications. Includes one (1) pair of expandable L bracket mounting rails to offer front-to-rear support of select rackmount UPS systems, or other heavy pieces of networking or power protection equipment with a 17.5 in wide rectangular chassis. A pair of expandable L brackets adjust to any setting between 20.5 and 36 in. The kit includes mounting hardware compatible with square-hole racks. Supports up to 500 lb.