They have been failing frequently, the output shaft shears off the top and the amp dies. They seem prone to vibration and according to JR are ok for a 50 size electric. Personally I wouldn't put them in anything that costs more than the servos themselves. The one I saw let go was on a 40 size airplane with 1 servo on each wing, not over powered and not set up for 3d. I just dont think its worth the risk on a heli that size.