Despite their small 3mm grub screws these GAUI pinions are OK with blue Loctite. I run this on my Hurricane 550 with a Turnigy Typhoon 500 motor and a 60T front gear for a headspeed of 2450rpm, on 6S4000. You must use use GAUI pinions as the Trex ones have a different pitch and will eat your nylon front gear ( I tried this) - Only GAUI 5mm pinions on GAUI 550's. Motor runs cool at 50 amps.