Therm-a-Rest Trail Sleeping Mat (Small) The toughskin's design sandwiches the mattress's air-holding seal between a top layer of open-cell foam Expandable foam: our patented expandable foam helps create a lightweight, compact core without waste Weight: 430 grams(15oz) Thickness: 2.5cm (1 inch) And a bottom layer of closed-cell foam, then joins them all with our guaranteed foam-to-fabric bond