Hey Mario, yes they are black Nylons and they sound awesome on my 77'!! The Nylon strings have a great tone to them and I'd like to order more!! I've also been using flatwounds over regular rounds for years now. I think that the flatwounds have always felt better on my fingers when I play and I just like the tone I get out of them more than I get from roundwounds. The tone that you get from flatwounds isn't so bright like regular rounds, which is how I like it. If you like a little brightness added as far as strings go and you want the best of both worlds from flats and rounds, you should try half wounds, although I've never tried them, but I've heard some good things about them.
(Message edited by bassplayer420 on November 16, 2012)