So I read all of these, and I'm wondering if anyone can explain the differences between:
Thermo-Lite 2.0 Bivouac Sac
Thermo-Lite Single Bivy Sack
Heatsheets Emergency Bivvy

They're all made by AMK, but range from $14 to $32. I can't see a big difference in the descriptions of them, so any help is appreciated!