A fellow athlete told me to size 1 up, and I'm glad I did. I ordered a Large whereas I usually wear small to medium depending on the brand. It's form-fitting and aero, not loose.- It provides great sun protection, stays cool, and is comfortable. Wicks sweat off really well. I do 1 hour to 2.5 hour runs with it in the heat, and pour water on the shirt to keep cool.- It has two pockets in the middle of the back, one high up (I keep my phone in there) and one lower down (for gels, etc). My friend says she's put ice in the pockets to cool down.- it's on the sheer side, so a patterned front helps. I get lots of complements on the manta ray design.- does not do well with safety pins for bibs, the holes left behind are bigger than you'd expect. I'd use a race belt if possible or pin to the shorts.I bought this as a recommendation from my coach for Ironman Texas. It is probably one of the best things I have done because it saved my skin from a scorcher out on the bike! 112 miles of sun, heat, dirt, and grime and I stayed cool through all of it. Wetting the sleeves kept me from wilting! And during the 26.2 mile run, I had volunteers put ice in the back pockets which helped keep my core temp down the entire time! It also helped to alleviate some of the achiness in my traps and neck from the bike. So, if you are doing any sort of races where you know it’s going to be absolutely and brutally hot - this is the top for you!