I had a chance to try out my Winter Sock from Dream Hammock this weekend. It worked great. I watched the temperature on my thermometer climb once I was all sealed inside the sock. As you can see the thermometer reads 58.5 with a -2 degree differential so more like 56.5. The temperature outside was 34 degrees. When I finally woke up this morning the temperature inside was 38 and outside was 28.