"Quote from Clark site"
Patented pockets for insulation (Four-season models):
The Clark North American is the only hammock that removes any need for insulating pads in most weather. The insulating pockets provide a stable air mass underneath you to block cold air from reaching your back.I hope that helps"Quote from Clark site"
The Z-Liner system fits four-season models to create a comfortable bed in temperatures below 32° F (0° C).
Cold Weather Ratings for the Z-Liner are difficult to specify since they depend greatly upon what kind of sleeping bag or quilt you are using inside the hammock and how whether you are a cold sleeper.
In general, the additon of the Z-liner should allow you to comfortably sleep at least 20° F (9° C) lower than you otherwise could. The Z-Liner has been thoroughly tested to work extremely well down to at least single digit temperatures (Fahrenheit) when deployed correctly.