The Rack-Mount Adjustable Shelf mounts to the front surface of front and back rack angles. The adjustable shelf support brackets are clear-plated 12 gauge steel and adjustable to fit multiple-depth enclosures or rack angle placement. THere are both solid and vented models available. They fit 19- or 23-inch rack spacing and require only 1U of rack space. Please note the load rating is for 150 lb. (68 kg).