I bought this in my usual size, wanting for the ultra-bright color. But it runs smaller than other PI riding shirts that I own, so my little pot belly is fully on display. I kept it with the optimism that maybe one day I will again be cut like when I was 25. HAH!Forget about layering under this thing, even if you're buff. Or buy a size up. It's a nice unit otherwise.Liked it so much I bought a second one. 6'5" 210 pounds 46 X-long jacket, 37 waist and the XL fits me nicely. It is long enough not to ride up in the back. Pockets are ample but not large. I wear this single layer down to 55 degrees - any lower than that I have to add a wind layer on top. Above 68 degrees this jersey starts to gets warm.This jersey is good for me down to a bit below 50. Then I go to a thermal long sleeve. It breathes well and has good pockets. Full length zipper is nice as well. As far as fit I have always had to size up for bike jerseys. I frequently wear a medium t shirt. I need a large bike jersey, but I expect this.I ride mostly along the Chicago lakefront and the wind can make it feel cool even when it's fairly warm. This shirt does a great job of insulating while being breathable - very good inbetween piece. I wear a 44R sport coat and the L fits perfectly, so this seems to be aimed at casual riders, rather than avid cyclist.Love it! Fits as expected, sleeves are quite long but no problem as you can pull them up a bit if you want them off your wrists. Zipper works great, easy to pull up and down with only one hand while riding. Pockets are large and easy to reach. Color is sharp.Wearing a good 10℃The optimal fit to the rating of the Pearl IzumiNice quality made for a casual ride not race fit very comfortableI'm 6ft about 220lbs. Bought an XL Fits perfect. Bought an XL.