OS Engines MAX 105HZ-R Nitro Helicopter Engine, 1.05 Size w/ Power Boost Pipe (Special order, enquire within)Enjoy huge power and performance with the compact 105HZ R! These are the engines that precision aerobatic and 3D heli pilots have been waiting for! In order for 90 sized machines to nail huge maneuvers and hardcore, smackdown style 3D it's all about power, and both the 105HZ and 105HZ R have it in abundance. Displacement has been increased by 15%, while a huge venturi rams air into the carburetor, producing massive power. Plus, they fit in a . 90