The Nemo Tuo sleeping pads have a thin film inside that weighs almost nothing and divides the pad into two separate airtight layers, each with its own valve. The base layer can be inflated firm for protection from rocks and roots, and the top layer can be inflated however much feels comfortable. Having two layers provides redundancy in the event of a puncture. Two layers also reduces heat loss by blocking convection currents inside the pad. The unique features of the Tuo series pads make them perfectly suited for harsh environments.