The Adams is a great American fly that works for all mayfly imitation. I can even get it working in a caddis hatch by snipping off the tail. I can use a size #8 for a hopper and a size #20 for midges.
It’s a nice bushy fly that works well in fast water, but sits just right in still water. I can’t think of another fly I can say all that about. Plus, it’s easy to tie and I enjoy doing it.