I bought this to replace a Patagonia pullover windbreaker that I've had for 17 years, used primarily for running. (It didn't wear out, mind you. I had purchased it to have a baggy fit, consistent with how I used to dress for running then, and I decided I wanted one with a slimmer fit. Styles change before Patagonia stuff wears out!) When I pulled this jacket out of the package, I couldn't believe that it could possibly block the wind, given how thin and light the fabric is. But this Patagonia product does what it says it will do! It helped keep me comfortable running in 15+ mph winds in Chicago in springtime (read: not warm, around 40F), with just a baselayer underneath. It folds up super small and takes up no room in a bag. My only suggestion would be to have a loop or something to tie down the hood (don't always need it), but I get around that by just tucking it in. Fits TTS. Great product, highly recommend.