Hiya...thats sure a good question because I have not found that answer either. I have seen both part # sold as M600 props. One thing I want to alert you to is to make sure you get the newer version of prop that has a pressed pin holding the prop in place , instead of the older hex screw. The older screws would crack and Ive seen an associate lose a m600 after one motor threw a blade. I did see another M600 user who instead of getting the new prop with pin, instead replaced the factory screws with higher strength screws.