Modfied motors have ball bearings, custom winds, and adjustable timing. Before purchasing any modified motor, be sure your speed control can handle the extra current that modified motors demand. Never use a modified motor with a mechanical speed control and always heed the manufacturer's recommendations for the number of turns your ESC can handle. Double, Triple, Quad, etc., refers to the number of strands in the wire that is used. Fewer winds usually equals greater rpm's and shorter run time.
More strands usually means smoother acceleration.
Smart racers know that it's not the fastest motor that turns in the quickest lap time. It's the one that is best suited to the track, car, and traction available, so choose the motor wisely if you decide on a hot modified. To get the best performance from your new stock motor, break in the bushings and brushes with Trinity's Bushing Buster and Revtech Comm-Drops. Always clean and oil your racing motor after each run.