Excellent fit, feels really nice. Just wore it on a 73 mile grav ride and never wished I was wearing a jersey.
Like other Ornot products I really have to dig to find something I do not love about the product. I am 6'1" 145 lbs with relatively long arms and the sleeve length and torso fit is perfect with a Medium. Head hole is smaller but should be fine unless you have a Costanza sized bulbous melon. My only real complaint is personal preference but the shirt is lightweight as stated and almost a base layer see-through consistency.
I purchased the size small. I'm a lady, 5'2" and 148 lbs. It's a good fit but a fit for a woman would be more desirable. The neck, sleeves and bodice fit well but not quite the feminine silhouette from a women's t-shirt v a men's. I am a very sweaty person and I am so excited that OrNot is offering a deodorizing top. I wore it on the trails and found it very comfortable. It is slightly rough, like merino wool. In fact, I had to double check the composition because it feels a lot like merino wool. I can't wait to see this top offered in a range for women and also for bike commuters. (I've stunk up a LOT of kit.) Add some eye-catching accents and patterns that make me dream about your jerseys.