Apollo propellers are highly polished, ultimate performance stainless steel wheels. The 993024 is a LARGE diameter right hand 3 blade, which is good for higher hp motors on heavier applications that require more diameter and blade area. 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.