I purchased four of these for my Quad. I removed the bells and balanced all four bells, I machined prop extensions that directly bolted to the top of the bells to insure that I did not lose a prop, then I flew with great success and the motors performed as promised. I then cryo'ed all four motors and the performance almost doubled. They ran cooler measuring 110 deg. F. and this is in the hot Southwest where temps were in the 100's for most of the summer. I highly recommend these motors, the performance and cost make them a easy choice.