The ULTIMATE extreme performance helical piston made of a 50% stronger polycarbonate resin, with embedded steel teeth specifically designed to work with Extreme torque up helical gears (ref#17164) to give a extreme heavy tuning of 170-190 m/s.All dimensions of the piston has been reworked to fit perfectly inside ULTIMATE gearboxes and gives a smooth low friction performance.The length has been adjusted to make a perfectly even contact between the first gear and the first teeth of the piston preventing breakage and minimizing wear.With ULTIMATE Extreme performance helical piston you get:Increased strength.Increased durability.Low friction.Perfect fit in ULTIMATE gearbox.Perfect combinations of polycarbonate teeth and steel for impact-energy absorption and strength.Optimal angel for first-contact between piston and gear.50% stronger polycarbonate (then ULTIMATE high performance piston)Reduced stress on motor.