Sea To Summit Ultralight SI Sleeping Mat Large"Light and packable for minimalist fast hikes" Our Ultra light S. I. Sleeping Mat is for ultra light hikers who can't go past the tried and true self inflating foam mats. The 2. 6 R value provides the insulation needed through the shoulder seasons while the memory foam means you don't have to exert yourself inflating your mat at the end of the day. The only mat in our S. I. range to come in an extra small size, it's easily fits into your ultra light