The 550 seems to be like the Levi's of yesteryear.  The fit is for an adult average male; don't let the relaxed part fool you into thinking that you should go a size down.  You should not these are true to size.  If you are a very slender person I would look for another LEVI jeans because this in an average man's cut.  Bought these as a gift, and they look great!  The wearer loves them.  You can get a way with the black as a dress pair if needed.