I picked up an ACE 1015 for my 4x4 Slash. The stock dbl arm would hit the chassis so I picked up a Dynamite single arm....it snapped after 1 1/2 laps. I cut up the stock arm that came with the servo so it would work. I did check that it wasn't over-traveling. SO, I was looking at Losi, Racers Edge, and HUDY but don't know which would be the best quality.