In its second generation, the Therm-a-Rest Prolite Apex Sleeping Pad boasts an unrivaled warmth-to-weight ratio for our year-round backcountry adventures. Its unique, two-inch StrataCore construction uses a continuous layer of foam between alternating ridges of foam and air to claim the best warmth-to-weight ratio of any self-inflating mattress currently on the market. Plus, the pad compacts down smaller than a paper towel roll making it the ideal companion for a comfortable sleep on our fast and light missions on the trails.