Marmot Trestles 30 Sleeping Bag Wave Construction - The Warmest Shingle Construction Available, Fitting Extra Insulation into These Bags by Creating an Overlapping Wave of Shingles Throughout the Bag. These Bags Will Keep You Warm and Dry in the Wettest of Environments SpiraFil High Loft Insulation, EN Tested 3D Hood Construction and Classic Trapezoidal Foot Box - For More Foot Room Compression Stuff Sack Dual Zippers and "Feely" Draw Cords