That is the issue German jacket liner, labeled "unterjacke". It's made out of goretex and is very similar to the stealth suit jacket, with a few minor differences; size of the hood, it has Velcro instead of snaps, etc.. Because it is a surplus item it is much cheaper than the stealth suit, you can usually pick one up for about 70.00. The big drawback is that most of them are used, so they will wear out quicker, especially along the seams, so if you can inspect the garment before you buy it, do so.