A chassis cab or cab chassis is a body style, and type of vehicle construction, often found in medium duty truck commercial vehicles.
Instead of supplying the customer with a factory pre-assembled flatbed, cargo container, or other equipment—the customer is given the vehicle with just "chassis" rails and a "cab". This allows the customer to assemble any desired aftermarket equipment—for instance, fire apparatus, an ambulance, towing equipment or a recreational vehicle conversion package—which can be customized for the specific needs of the customer.
Aftermarket equippers, including coachbuilders, often make their own packages that can be ordered for the truck.