The Sport Rider 4 is a heavy duty 4 bike capacity rack that will fit almost any style of bike using a padded universal top clamp and adjustable wheel holders. Simply drop the bike into the wheel holders and secure the Velcro wheel straps, then slide the self-locking clamp down onto the frame to secure the bike. For ease of use, the Sport Rider 4 comes out of the box set up as a two-bike base unit. The two-bike add-on kit (included in the box) is easily assembled to the base unit.