I've worn the thermal jersey in the size XXS, and it fit perfect, so naturally I ordered the same size in this wind jacket. But it came out tighter fitting than the jersey (naturally the fabric is not as stretchy too), when yet you might expect it to be larger to go over other jerseys/jackets. I very much agree with other reviews, it is very small in the arms. No pockets holes either. Note: I'm 5'1" weighing 110lbs, have rather slim arms and 32 chest

I love the color and the idea of this jacket. As someone who frequently visits places with hot weather, this is a nice jacket to start you off if it’s misty cool in the AM, and as you warm up, you cool off with the ventilated sections. My one thing is that it would be awesome if this was made for UV Protection and hot weather in mind. I felt like I could have benefited from a different material in the underarms section. If you wear any antiperspirant, it immediately shows on the garment which is made of the front material, not the back mesh. If and when Specialized creates a “summer UV protection” line, it would be nice to see these in light colors to reflect the hot summer sun instead of absorb them. :-)

Love the color and the material, however, if you have muscular arms of a bigger bust you might want to size up 1 or 2 sizes.

This jacket is so high quality and I love the stretchy mesh on the arms and back. I am 5'10'', 158 athletic build & medium tops typically fit perfect. I ordered this is a large so I can wear layers under it. Even without anything underneath, this runs super tight in the shoulders and arms, so when I'm in riding position, the jacket cuts off circulation to my arms. Will be exchanging for an extra-large. If you have an athletic build and muscular arms, I suggest sizing up!