Why purchase a HeatStore sleeping bag over a standard reflective sleeping bag? Here are three big reasons. 1. Durability. If even a small tear occurred with a standard reflective material, there is little resistance to the propagation of the tear across the entire length of the sleeping bag. A sleeping bag with a big tear does not do much to retain heat. Our NEW sleeping bag uses a layer of aluminumized PVC bonded to a layer of thin non woven nylon fibers. The sleeping bag remains very thin and lightweight, but more resistant to punctures and more importantly, the propagation of tears. The seams are reinforced with the same multilayer material for added strength. Standard reflective sleeping bags use only tape on the seams. 2. Heat Absorption. Standard reflective sleeping bags are reflective on both sides. While the standard reflective bag reflects heat from the body back towards the body, the outside is also reflective and reflects heat from the sun away from the body too. Our multilayer sleeping bag will absorb more heat from the environment rather than reflecting it away. 3. Visibility. The orange outer layer is visible from long distances and contracts with snow and trees.