Our Overload/Underload Training Pack is comprised of an endloaded overload bat, a knob loaded overload bat, and an underload bat. The target weight differential on these overload and underload weights is +/- 10-15% of the drop-3 weight of the selected length.
 
The end-loaded overload bat is cut to a +10-15% weight and is not cupped. The intent with this is to provide an overall greater weight while also shifting the center of mass furter toward the barrel of the bat. 
 
The knob-loaded overload bat is cut to be a finished weight of +10-15% greater than what would be expected from a standard bat in the selected length. There are approximately five ounces of weight below the knob, but above the pivot point of the bat during the swing. This shifts the center of mass towards the hands, providing a different feel for the bat and aiding in accelarating it through the zone. 
 
The underload bat is cut to be 10-15% lighter than a typical bat at the selected length. The change in weight, however, is evenly distributed throughout the bat.
 
The profile of all three bats, excluding the mass below the knob of the knob-loaded overload, is that of the Pro GLB 85.