I to have had so many problems with hitech servos I WILL NEVER BUY ONE AGAIN!!!! They have problems centering & sticking,The models I have had problems with are 605 bb, 625mg,645mg,and the 425bb,I have now switched to airtronics & jr servos with no more centering problems.The radios that I have been using are good radios,mx-3 & m-8.