WJ 4U, 6U, 9U, and 15U 600mm depth simple racks are built with high-quality aluminum/ steel structures and are ideal for countertops or under desk applications. These units are lightweight, stackable, and completely portable; therefore it is easy and simple to stack up an additional system when more space is needed. Running out of rack space may never be an issue again. With spring loaded recessed handles and casters (Casters Included), these simple server racks provide your critical rackmount equipment the ultimate mobility and maximum portability.