The Mountain Hardwear UltraLamina 45 is extremely lightweight and highly compressible. A perfect combination for a light and fast trip during mild weather. With welded construction and ThermicMicro insulation this sleeping bag will maintain loft even through repeated washings and compression cycles, and the insulation will not separate causing cold spots. This is a great bag for backpackers looking to shave weight without compromising comfort and warmth.