Durability: well it’s designed for use in action, but like anything it’ll rip if caught on say barbed wire. It’ll be the standard Gore, not Paclite or anything fancy so with normal wear and tear they’ll be pretty robust. We’ve been through phases of lightweight, then heavy harder wearing, then back to lightweight (2 layer – 3 layer – 2 layer). If you want really tough then you need some of the trousers from the late 90s, early 2000’s. TBH though it’s probably not make that much difference.
Sizing: issue kit is sized in centimetres, not inches, so you’ll need to know your waist size in cm. We also size for seat and inside leg – when you look at the tab you’ll see something like 12/34/56, this is the waist/seat/inside leg in cm.
Bear in mind they won’t have fancy pants stretch panels or anything like that either so you may find the back of the waist being pulled down by pedalling/moving around in the saddle.
TooTall’s comments about other nationalities’ kit is a good point, especially the bibs, but bear in mind, in general, everything will be much of a muchness in terms of material, durability, etc, it’ll just be the camouflage pattern that’s different (I used to use a Dutch DPM Goretex liner years ago and was given some American kit last year when I was attached to them). And some surplus stores might add a mark up for “exotic” foreign kit…