The Base is selected per the Servo you have. For example, if you have a Logitech wheel, you would get a Logitech Base. This Is installed and stays on your wheel servo and serves as the Male end of the quick release system. All Bases include a Bolt. Prices are determined by the amount of material used to make the item. After selecting your Base, go to Quick release wheel adapters and select the wheel adapters you will use with your base. To view a video on the quick release system see the Videos tab at the top of the page.