Just received this jersey from BT and on the listing's advice I ordered up a size and went for the large. I'm 6' and about 145-150, pretty skinny up top, and the large was just way too big. I sent it back and I'm going all the way to a small. Another Castelli jersey I have (in a medium) also fits a little on the loose side. Not sure why everyone says these fit small. I have t-shirts smaller than this large jersey. Seemed like a quality jersey otherwise though! I'm anxious to get one back that (hopefully) fits.