Again DriveDen had a range of options. I wanted the option to carry up to 4 bikes and a twin pack helped reduce costs. I found these really easy to fit and attach the bikes to. I would suggest once you've fitted the bikes take a short test drive. I found going a mile showed the clamps just needed a slight adjustment to get them properly secure after which they were solidly attached to the roof bars. The main brace which fits against the bike down tube dictates where the wheels will be positioned and the brackets that secure the wheels move to allow for adjustment for different size bikes. Also the carrier can be locked with a key to the roof bars and the clamp holding the bike down tube also locks with a key. I've fitted 2 carriers so far with the option of another 2 once my younger son and wife want to join my older son and myself. They are easily removed when not in use.