honestly... the United RC stuff in kinda ghetto. it doesn't come with the alum. slider and the screws that come with the motor mount are too long to be used on their own... if you use they're heat sink the screws are fine, but if you don't you need to go out and get some washers..
don't get he heatsink either cause the guy said in a few weeks they're gonna re-design it to fit on top of the motor better... its like "do the sh*t right the first time"..
I just got my XRAY alum. motor mount. the thing is beautiful, extremly high quality, looks like a laser cut it.
if you can't find an xray mount or you don't want to wait get the
www.ipdracing.com mount, it comes with the slider.
www.avmracing.com also sells a nice mount with heatsinks cut into it.. but they're outta germany and the customer service is kinda iffy..