This "ventilated" shelf firmly attaches to both front and rear rack rails and occupies only 1 rack units of space. Vented cut-outs are individually 2-7/16" x 3/16". Depth is adjustable from 20" to 32". Weight capacity is 150 pounds. 8 each 10-32 x 5/8" steel mounting screws are included. Shelf weight - 17 lbs.