Here's a favourite of mine - the Micro Dun B. rhodani version. I've right now tied half a dozen of these during the last half an hour. Every year I tie hundreds of these. A really great consistent fly for brown trout rising to rhodanis. Look no further when the big browns are rising to rhodanies mid May.
If you noticed the hackle, I have dyed a light barred ginger rooster saddle in a olive-dun-brown colour. Veniard colours. Mostly dun, a little olive and just a hint of medium brown. Just about perfect :-) Not that it's important at all, but for me - it is in a way. In a way. Sort of. Tie the hackle with a medium dun colour and the trout won't see the difference.
I also fish this hatch a lot, and have a special dubbing blend that I use for my Baetis rhodanies. For me this is what-I-need, but in fact it is just 4-5 different Fly-Rite colours of pretty similar dyes, and probably not so important that too, I guess. Tie with a light cream-olive blend and you are spot on (yes, light - look underneath the small dun abdomen, and you'll see it's much lighter).
Rhodani's?
I like 'em :-)