RED LINE – Extreme Power Model Engine REDLINE is a new engine product line of Thunder Tiger. high performance, extreme power will be the main features of this series engine. With the biggest displacement and awesome power, RL-53H is the best nitro power plant for your 50 class R/C helicopter. The XC2 is extreme composite coating of nano-technology from Japan to make the engine life longer.And the special criss-cross pattern is etched on the sleeve wall to reduce the friction. With these technologies , the RL-53H will produce reliable power and torque even at the high RPM. The all-new designed carb is mounted to the crankcase with a heat insulator to keep the carb working at stable temperature in different conditions.