So you are saying Deere has Claas manufacturing parts for them? If so, Claas must do it better or cheaper than other vendors.

The JD cutterhead, feedroll and accelerator are definitely not the same parts used in Claas choppers. Designs are not even close. At least not the last time I looked, which was probably at least 2 years ago.

I have a Kooima feedroll in our Claas. Does that make it the same as a Kooima chopper?

I didn't/don't want this to be a JD/IH or Ford/Chevy color war BUT there are differences in the design of the different units. When you buy a brand, you are buying the design, not the specific part vendor. Everyone outsources to some extent.