UPDATE: My warranty replacement top also quickly developed giant holes all over the place no matter how gently treated, hand-washed, and stored (while my other brands are fine; it's not moths). My brand new Meriwool beanie ALSO has similar holes. I'm done with this company; their products are too fragile. I advise everyone to pay a little more for quality name brands like Smartwool and Icebreaker.OLD REVIEW:I bought this top for use as a base layer on colder runs (under 20F) due to wool outperforming polyester in warmth, comfort, wicking, and smell. The medium fits my 5'11" 165lb body well, being almost but not quite skin tight, and with a perfect arm length. Love having the half-zip option as it makes regulating temperature while running that much easier.Unfortunately, I discovered a dime-sized hole in the top after a single wear, and I was outside of Revain's 30-day return window having bought it earlier in summer. FORTUNATELY, Meriwool has a 1-year warranty, and they actually honored it instead of weaseling out of it, which earns major respect in my book and is the impetus for leaving this 5-star review. You simply need to send them a photo of the defect, your order number, a screenshot of the order, and then they'll provide you a RMA pdf form to fill out for the exchange. You pay return shipping, and that's it.While I was waiting for the exchange, I ordered a nearly identical half-zip from Meriwool's competition -- Smartwool -- at nearly double the price to compare. Turns out I actually prefer Meriwool's half-zip for two reasons besides just being a better value: 1) Meriwool is a tighter fit for sweat wicking vs Smartwool (also a medium), and 2) Meriwool's collar doesn't awkwardly flop around when unzipped like Smartwool's does. Will definitely be buying more in the future for casual wear vs only winter running.