And they're fun to play with. Being 7s, the 6 non-threaded sprockets can be replaced with 8s HG sprockets when worn out. Before that, however, one can simply turn the sprockets around and wear the other side out. I haven't ever fully worn a sprocket out. One could buy a cheap 8s cassette with the desired teeth and use the threaded locking sprocket to hold everything on. Until Loose Screws went all Second Amendment on us, it was a good source of threaded 1st position UG sprockets. They can still be found on the bay, too. Just be sure you're not getting DA sprockets, those are a whole 'nuther can 'o worms.