These bibs are built ridiculously well. It's typical Arc'teryx craftsmanship, but I think they went above and beyond on these bibs. Based on the tough material these are made of, it's hard to believe they will ever wear out - and I hope they don't. They're completely waterproof and extremely comfortable in a range of temperatures, which must mean they breathe very well. I've used the side zips (water-tight when closed) to vent in warmer conditions and they work great. I wouldn't recommend taking a seat in the pow with the vents open though. I managed to fill most of my pant leg with some shockingly-cold pow when I forgot to zip the vents back closed. Can't say anything bad about these bibs - I'd give 'em more than 5 stars if I could.