Not all camps are made on lush meadow grass, thats why Thermarest designed the Toughskin Mattress. Toughskin is a puncture resistant bottom consisting of closed-cell foam laminated to the air-holding open cell foam above. Sharp objects may penetrate the outer fabric but the closed-cell foam is thick enough that the chance of a puncture is remote. Its a great choice for use in places where thorny debris is common, sleeping out on abrasive rock slabs, or just making sure that your mattress holds up during a lengthy expedition. The Thermarest Toughskin Mattress is field repairable, even in the unlikely event that it does puncture. It also offers an R-value of 3.5 when deflated, which is in the same range as the fully inflated Thermarest ProLite 4 mattress series.