Thinsulate is a type of synthetic insulation that was created and trademarked by the 3M Corporation. It first entered the market in 1980, and has become the standard material for boot insulation.

Thinsulate is highly effective due to it's super small fiber size. Typical Thinsulate fibers are about 15 micrometers in diameter, which is about twice as small as polyester. Although smaller and lighter, Thinsulate fibers are more dense and significantly thinner than polyester. Being so thin, Thinsulate fibers can be woven more closely together which reduces the flow of heat away from the body and allows moisture to escape and evaporate.

Those insulation properties make Thinsulate the market leading choice for boot insulation. Thinsulate can be woven into the boot membrane without adding any significant bulk or weight.

Thinsulate is usually listed in boots by the gram, and can range from 300 grams up to 1800 grams. The lower the amount of Thinsulate, the less insulation that the boot possesses. Higher amounts of Thinsulate provide more insulation and warmth for colder weather.

What's the optimum amount of Thinsulate for your needs? That will really depend on the climate that you hunting in. For hunters who are hunting in the Southeast and won't generally experience temperatures under 20 degrees; 400 to 600 grams along with a good pair of wool socks will work fine. Hunting conditions where the temperatures are under 20 degrees, will usually need 800+ grams of Thinsulate.