I have been reading about them for some time. I have a WM now and am very happy with it. But am considering getting something new to shave some o z's. I think the Montbell stuff is priced better. Anywho, the stretch bags I had before were both synthetic and jsut thought someone might know the tech specs on this. It might be a little critical, at least for some degree of comfort, since I plan to push this bag past the limits.