So I'm about 5'8", weigh 155 pounds, have a 30" waist and I ordered the small model. My chest is about 38 inches and this fits me perfectly! I've had tanks from many other companies including J Crew, Target, Banana Republic and they really do fit the best, are softer material and don't shrink too much in the wash. I have actually ordered 3 more which I highly recommend.
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