In reply to Ginger McGrath:
I've been using them for years. They're like powerstretch but with a significantly stronger elastic element. They get used for winter climbing under softshell trousers. I also have a pair that I wear on the bike and another pair that have been cut off below the knee for the OMM. They last for years and years. They dry fast when wet, and they're warm on a bike in tipping rain.
As mentioned, there's no fly, but that's hardly the end of the world.