These are the engines that precision aerobatic and 3D heli pilots have been waiting for! In order to nail huge maneuvers and smackdown-style 3D with your 90-sized machine your engine has to have power, and both the 105HZ and 105HZ-R deliver. Displacement has been increased by 15%, while a huge venturi rams air into the carburetor, producing massive power. Plus, they fit in a .91-sized mounting pattern. The machined, blue anodized heatsink head is light in weight, and cools the engine efficiently. An extra feature on the 105HZ-R is the pressurized DRS (Demand Regulator System), which ensures consistent fuel flow regardless of the heli’s attitude.