That's the additional ground clearance you'll get with this rack, giving you extra clearance for getting your trailer or RV up driveways, curbs, and anywhere else approach angles are a concern. 3D wheel trays with additional rubber straps keep bikes securely in place, secured by telescoping hooks that secure most bike frames. When it's time to put the Nomad into storage, the clamshell design allows the wheel tray arms to fold up, making it narrow enough to fit into even the tightest storage space.