The Autococker Trilogy is truly amazing marker. The problem however is that it is not adjustable like it like the its predecessing Autocockers. The Shaft Kit was designed to change that. The Shaft Kit allows you to correctly time the Trilogy. to correctly time the Trilogy means to fine tune its cycling timing. Proper timingIt reduced ball breaks as well as allows for higher rates of fire. In essence, you can achieve the shortest trigger pull possible and shoot shoot more people all at the same time....life is good.