If you are refering to the chopper rotor itself, Rodono makes a nice one with flails. As for the original chopper rotor I don't really know of any aftermarket knives of a different design. There are alot of aftermarket sections available for chopper concave that are more aggressive and use knife sections. We make our own around here. Main thing for chopper hammers is to keep them in good shape. Once they get rounded, they won't work as good. I have tried building edges up with hard surface weld, and that works pretty good. I will be trying a set this year on a combine that were cryogenically frozen to see how that works. It has worked good on knife guards and threshing elements, so I don't see why it won't for chopper blades also.