Truck caps are a shell-like structure that can be placed above a truck bed. The cap provides additional vertical room for the cargo in the truck bed versus a typical bed cover. Most truck caps are typically made of either fiberglass or aluminum and can be customized for the make and model of your truck.
Fiberglass truck caps are generally made specifically for your truck make, model, and year. This allows the fiberglass cap to fit around the cab of the truck for a more contoured look. Though fiberglass caps are typically more expensive than aluminum caps, they can match the paint code of your vehicle as specified by the truck manufacturer.
Aluminum truck caps are less expensive than their fiberglass counterparts. They may also be heavier than fiberglass caps and generally come in standard colors. Most aluminum truck caps are made from a standard mold and may not contour around the cab of your truck, so the front of the cap may be taller than your cab.