2 Post offers a variety of sliding or fixed shelves for 2 Post racks. They are able to withhold weight from 30lbs (14kgs) to 900lbs (408kgs). Also the shelves are compatible with threaded, square, or round hole racks, while giving an adjustable mounting depth. 2 Post shelves are designed to hold all types of equipment in any size or weight. The 2 Post Heavy Duty Rack Shelf- 21” works with any 19” rack and can be mounted up-side-down. It can hold up to 300 lbs (136 kgs) and devices 21” (533 mm) deep. The shelf is made of 14 GA steel and has a surface area of 17.7” x 21” (450 mm x 533.4 mm).