The POWRTOUCH ALL WHEEL DRIVE TANDEM, mover drives all four wheels of the trailer. This model is required where a heavy tandem axle trailer may be used on a steep slope, turning up hill, or on uneven ground where the drive wheels may lift of the ground. It will fit the majority of tandem axle trailers. When installing this model of mover, special attention should be paid to any heating or water pipes that may interfere with the installation.