Delta PRO Aluminum Innerside (Lo-Side) Truck Boxes utilize the Gear-Lock™ System, Self-Centering Latch Pin, RSL™ Lid and High-Strength Body Design. They mount on the top of the bed side walls and are ideal for storing longer tools and equipment. Innersides help keep the bed free for storing bulky items. Combine with a Crossover to create a wrap-around storage system.