Therm-a-Rest Trail Pro Mattress Large Added Warmth: Diagonal-cut foam increases warmth without adding weight Superior Comfort: Two Inch (5 cm) of supportive loft, plus a semi-rectangular shape that offers gapless coupling of mattresses Light Weight: Our proprietary, vacuum-poured foam keeps weight to a minimum while delivering exceptional packability Self-Inflating: Expanding foam core self-inflates; top off with just a few breaths for personalized firmness. R-Value: 4.0