This heavy-duty sliding adjustable shelf fits in a standard 19" rack mount cabinet. It's constructed of 14-gauge steel and is vented for increased airflow. This shelf supports up to 125 Lbs. The mounting brackets on the sides adjust from 12" to 31" in 1/2" increments to accommodate a wide degree of rail depths. The 29"D shelf will slide out 18" from the front rails of the rack or cabinet when fully extended, making it ideal for accessing the back of servers and other equipment.