The Apollo 4 blade propeller is designed to improve hole shot on heavier loads. The 993204 is ideal for pulling and towing in water sports. Apollo is designed to use Michigan Wheel’s XHS hub system and is interchangeable with the Mercury Flo-Torq II hub system. If you chose a hub kit, either the XHS or Flo Torq II will be supplied. FREE SHIPPING! If you’re not sure what hub kit you need–please call or email for help.