The Silverton 25 mummy bag is great to use in cold and extreme weather, as well as backpacking, and very snug fit for increased warmth.
Tall Mummy bag
Thermolock insulated, full length draft tube prevents heat
Loss through the zipper
Zipplow no snag zipper
Double-batt, offset quilt construction eliminated potential cold spots
Cover: Polyester rip stop
Insulation: 38oz coletherm fill