I have a Roman Palm IV which has worked OK for me. Use it for summer and on the boat.
Have gone into sub zero on 1 occasion, had to wear my thermals, socks and a hat to keep the ice that rained down from the inside of the fly off my head.
Oh they are not waterproof either got damp (not cold) feet when I slipped down hill and my feet pocked out form under the fly in the rain.
Over all for the price they are good. Not suitable for larger guy's.
Zq
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