Michigan Wheel’s Xchangeable Hub System absorbs impact and stress caused by shifting gears and is designed to spin under significant impact to help protect your lower unit. XHS / XHS II is also designed to be interchangeable with Mercury’s Flo-Torq II hub system, potentially saving you money when replacing or upgrading your propeller. Michigan Wheel’s XHS Hub Kits are designed for use with the Vortex and Apollo Series propellers.