Here's what 3M has to say about Thinsulate:
http://solutions.3m.com/wps/portal/...n/Homepage/Product_Information/Footwear/I had a saleswoman tell me that rating tells you how cold they were rated for (while
actively moving):
Thinsulate 400 = -40 degrees F
Thinsulate 600 = -60 degrees F
Thinsulate 800 = -80 degrees F
etc.
She said that was the rough scale but that the manufacturer was was a little on the generous side. Being a salesperson, she may have just been fed B.S. or was feeding me B.S. I personally didn't put much stock in it.
I was doing a January cow elk hunt between 8,000 and 11,000 feet so I went with some Thinsulate 800 boots. I've warn them in -12F weather up to 55+ F weather and never once noticed being uncomfortable due to cold or hot feet. I also wear wool socks with them to help wick away any moisture.
However, I think for most of my hunting I'd be fine with Thinsulate 400 or 600 too.
