The material used in these bibs seems very durable. I usually wear a large but I got x-large and they are quite snug. Very warm also.
Be forewarned - if you own previous versions of these bibs, they are NOT as warm as earlier iterations when worn alone. I was surprised and disappointed to find this out in my first ride with them, that they struggled to keep my legs warm on a road bike ride once the mercury dipped below 40deg Fahrenheit, even with non-stop pedaling. They don't block the wind as well either, you can feel a fair amount of it through the AmFIB, including the crotch area.
You'll still need to size up over your normal waist size to get them up to your waist. Fit is snug, but not unduly binding and they require some work to get past the knees, but it's not horrible. While the chamois has been beefed up, it's bulky and I found myself shifting around on my saddle too much because of it and it doesn't really add much in the way of comfort over previous versions.
Tights fit well (I'm 6'2, 160 lbs) - not too tight, not too loose. I am comfortable from 50 degrees to 10 degrees (with suitable layers on top and good socks/gloves). They seem to be well-built -- I'd certainly buy them again and recommend to cycling friends.
This tight replaced an older version that I have had for about 6 years. Rode a couple of times in 40 degree temps and was plenty warm. I am 5�11 165 and the large fit well although the straps could have a little more stretch. Fabric had more stretch but is still stiffer than just the thermal tights, pad was comfortable on 30-40 mile gravel rides.
