The difference is the "replacement pin" (or whatever Shimano calls them) that you use when you are joining the ends of the chain together. The 7801provides slightly more positive "feel" when you are pushing it into place with the chain break tool. With the 7800 pins many people didn't get them seated correctly, and then they had problems with chains breaking (i.e. coming apart) under use.jwelch said:Have noticed some D/A chains are 7800 and some are 7801. Any imput to the differences? Thanks!