These pants fit incredibly well!!!  We bought the 6 Slim for my very thin 7 year old.  He could wear 4T in the waist and have room.. but pants are so tough, because he is so tall and skinny.  These were PERFECT.  The quality is exceptional.  I can tell these will last a while.  The length on the 6 Slims were perfect for my son, who is 48in tall.  The waist has an adjustable band built in, so we could tighten it up a bit, and it didn't look bunched up or awkward.  The hips and legs are straight and slim-cut, so he isn't swimming in extra material.  Seriously.. we bought 4 pairs to use as his school uniform pants.  Then bought 2 more in the next size up, in case I can't find them next year.  Perfect!