The rubber end will be smaller on the end for a tighter fit. Make sure to apply some synthetic grease on the spline shaft end, this will help it slide on better. Double check your impellers: too high of a pitch will bog your motor down on hole shot but will provide higher top end, lower pitch will increase hole shot but reduce top end. If for instance you are replacing your stock impeller with a solace, it will appear alot different. Solace impellers differ fom stock ones.