I've had this jacket for a few years now and it never really quite held up to expectations. As it is 70D, it's not surprising that it doesn't breath well, even with side zips open. The breathability depends on how much you sweat or what you're using this jacket for, which isn't the jacket's fault necessarily but just something to keep in mind. My main issue with this jacket is the fact that it wets out very fast. Even with using Nikwax to boost the outer layer's water resistance. It never beaded water for very long. As far as fit is concerned, I wish I had ordered a size up. It's tight across my chest and shoulders. I In conclusion this jacket is good for light rain but I wouldn't trust it to do much else. It would be helpful to the consumer if products had the breathability ratings, in order that the consumer may be more aware of what exactly their buying and the protection they are investing in.