In reply to Mostin3:
For what use?
- Just in case. Superlight, cheap, non-breathing, alluminium coated inside to reflect heat, hopefully keep you warm enough so you won't die; AMK SOL BIVVY (Mylar like bag, but a different laminate which is stronger/silent)
- Cheap, durable and breathable; old army bivvy. Build like a tank, but weights like a tank too.
- For planned trips, i have a (discontinued) breathable Wafo bivvybag, which has a long zipper in the middle. Allowing you to craw inside it much easier and allows you to control the airflow, when you get to hot or need to get rid of moisture.