DESC: The Big Agnes Horse Thief Sleeping Bag was designed for today's light and fast backcountry crowd. At 1lb 8oz, the 725 down fill Big Agnes Horse Thief is a crazy light 35F bag. Big Agnes makes sleeping bags without insulation on the bottom of the bag because down and synthetic insulation compressed by your weight loses virtually all of its insulating value. Instead, Big Agnes puts a sleeve in the bag floor into which you slide your sleeping pad, and the top 2/3 of the bag is insulated like a traditional sleeping bag. This system offers several major advantages: 1.An air or foam mattress provides more warmth than compressed insulation. 2.You're guaranteed never to roll off your sleeping pad in the middle of the night. 3.It reduces overall weight of the bag, and therefore your pack. 4.The bag and pad can be stuffed together for compact packing. Compatible with Big Agnes 20in wide Mummy sleep pads.