Tron makes great helicopters and their innovative design for these motor pinions and motor mount system works excellent. These pinions are strong, durable, and work exceptionally well. I set up my Gemini helicopter a little different than I have with my other helis in the past. I went for a lower kv motor and a higher tooth count count on the pinion to see what kind of performance, efficiency, and flight time I could get. The Xnova motor I purchased had a 5mm shift and I needed this 17T pinion to put on it and get the head speed at the desired throttle percentage I wanted.