Provides centered loading for deeper and heavier equipment. Mounts on 3"D (80 mm) double-sided racks only. Mounting hardware not included. 19" version holds equipment up to 17.75"W x 21.5"D (450.9 mm x 546.0 mm), 23" version holds equipment up to 21.75"W x 21.5"D (552.5 mm x 546.0 mm). Made of strong, lightweight aluminum; supports up to 100lb (45.4 kg). 19" version is UL Listed: File E140851; Category DUXR (US), DUXR7 (Canada) - Communications Circuit Accessory.