Do not buy cheap servos, especially the tail servo. Do not buy cheap servos full stop. I have checked all the servos on a first build after what I would describe as a firm landing. Every one of them had been stress at the mountain lugs to such an extent the plastic becomes brittle then breaks. The servos I believe need rubber mounting grommets to absorb the vibrations and some of the shocks of general flying especially when a newbie. This is another lesson learned the hard way. I.E. through the wallet. The servos I brought were probably good in a glider but definitely not in a helicopter.