I got this for my 11 year old son.  We got him a size large.  It has a snug fit with just underwear underneath.  He is about 4'9" and weighs about 90 pounds.  He has really enjoyed this costume.  We bought for Halloween but he has worn it already several times.  The mask is a bit flimsy, but he has another mask that is more durable.  We took heed of other comments made about his costume and are careful getting in and out of it since there is limited opening in the back.  So far we have not had any issues with tearing or breaking of any part of the costume.  The cost is great - especially compared to the same costume from Party City.  Thanks for the other reviews and to Amazon for offering the exact same product as our local costume store but for a 1/3 of the price.