The air chambers are filled with 150 gsm Texpedloft microfibre insulation, so you not only get a comfortable, ground leveling mat, it keeps you warm down to minus 17 degrees Celsius. This means you can afford to take a lighter sleeping bag, keeping your pack weight to a minimum. The laminated polyester outer is waterproof, air tight & very durable. Twin valves make inflating & deflating fast & the built in pump, once mastered, inflates the mat very quickly without introducing moisture to the filling. A sleeping bag is only as good as the mat it lies on, once you get in your sleeping bag you compress all the insulation that’s underneath you, rendering it practically useless. Therefore it is essential to have a good insulating mat to protect you from the cold ground.