EricBwrote a review of Flylow Magnum BC Pant - Men's on January 29, 2014
Familiarity: I've used it once or twice and have initial impressions
Fit: Runs large
I only have a few days with these pants, but I can share some design/fit information.
I am 5'9" 165lbs 33x30 pant. I tried on both the Medium and the Small, and went with the small. I could have gone either way depending on if I wanted a very loose vs. traditional fit. They fit slightly slimmer than my Patagonia Snowshot pants, and are shorter so I don't step on the cuffs in the parking lot.
The material doesn't have much stretch to it, but I suppose there is some. The pockets zipper down to close which takes some time getting used to. The outer leg zips are awesome, but start an inch from the top instead of 12" down so they look a little odd when unzipped. Inner's are great.