The surplus bivy was originally designed to be the outer layer of the modular sleeping bag system. The system allowed the soldier to use multiple combinations of the two sleeping bags and bivy sack to be comfortable over a very large range of temperatures and conditions. I was only concerned with the bivy as I already own a few sleeping bags that I am very happy with.
|Empty bivy sack.|
The material is probably the heaviest GORE-TEX I have ever come across. The huge dual YKK zippers can be used from the inside or out and can be opened to allow for venting. There are also some really heavy duty brass snaps that the sleeping bags from the modular sleep system snap into. This was so a soldier could get out of the bivy real fast should a combat situation arise while they were sleeping. For my purposes, they fasten the storm flap over the zipper.
The zipper stops just above the shoulder when you are inside and the hood fastens down with a square of Velcro. I read many reviews that complained about the hood not fastening properly and allowing rain to get in but in the field I have not found that to be the case. I have used this bivy in rains that would soak my Kelty tent and it has completely surpassed my expectations.
|Western Mountaineering Alpinlite 15* bag and a Big Agnes Insulated Air Core both fit inside.|
The bivy is made by Tennier Industries and is 100% GORE-TEX.
If you are looking to dip your toe in bivy sack camping and don't want to spend to much to see if you'll like it or not, I highly suggest getting a US Military Surplus Bivy. If you are like me you'll find that there is no need to upgrade to something lighter and you will take comfort in the fact that you have purchased what is probably the most rugged bivy sack on the market. Your tax dollars were already spent creating this product so you should take advantage of it.