The Rhino-Rack Backbone is a mounting system for your Toyota Tundra Crewmax. It connects to your vehicle's roof via 3 bases on each side, and allows for a Rhino-Rack Pioneer System to be fitted on top. This makes it easy to carry all of your gear on your Toyota Tundra! The Backbone is designed for your TOYOTA Tundra Crewmax, allowing you to carry more on the roof with a Rhino-Rack Pioneer System. Connecting via 3 bases on each side and a base at the cab end of the chassis rail, it's a simple way to mount a roof rack onto your vehicle.