At 5'6" and only 114lbs, I took a chance and ordered my usual Pearl Izumi size,SM. Though fit and competitive I have always been very slender and even my best shorts look kind of, well, er - LOOSE. But when my order arrived (very prompt) I was surprised by the very nice but TINY look of the shorts - like something for a 10 year old junior racer! I tried them on and they were VERY snug but fit like a fine glove...here's what I like after several rides in the Durango CO area - when I am in the riding position they are a perfect natural fit; no tight spots or bunching where you might expect. The Progetto X2 chamois is very comfortable, made of different densities and extends unusually far foreward - perfect for riding in the drops or descending. These shorts are very well made and the design very well thought out - and for me more comfortable than bibs. Probably not for everybody and Not Free(cheap) but very very Aero!!