Why 105 mph?
Obviously, nobody throws or needs to hit a 105 mph pitch, and we don’t recommend the machine be used at that speed. However, to throw a 90 mph fastball with realistic backspin, you need to set one wheel at 105 and the other at 75. Same thing on a 90 mph slider. To get the ball to spin properly, you need to set one wheel faster than the pitch speed and one wheel slower.