The semi 4.0 is a zero frame contact rack. It is ideal for carbon frame bikes. The design is sleek and simple; the pivoting arm with ratcheting hooks tightly grip the bike by the front wheel and the back wheel is secured with a ratchet strap that will hold the bike in place. This rack fits most frame sizes, shapes and styles; it fits 20" - 29" wheels and can accommodate a wheel base from 37" - 50". the long folding pin function allows this rack to fold up flush against the back of the vehicle. This rack is user friendly, quick and easy to assemble. The semi 4.0 is equipped with integrated locking cables so that you can lock your bike to the rack. The rack has a sleek, modern design with hints of green make it an attractive rack with aesthetic appeal. This rack is a rugged combination of strength and versatility. It's finished with a powder coat that is durable and rust resistant. It has a limited lifetime warranty. Get the semi 4.0 add on (#64699) and transform this rack into 4 bike carrier.