I have the hs-645 servo on my stock emaxx, it has one of those spring servo horns and it works ok but i just put on some aluminum beadlocks with jumbo claw dawgs on it and it winds the spring alot lol so i'll change the wheels back to something else. im gonna save up for the 333oz servo for my aluminum e-maxx. I thought i might aswell cause after i get that i'll never need another one, and i'll get the supermaxx servo saver :)