Marmot Trestles 15 Degree 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 EN Tested Classic Trapezoidal Foot Box - For More Foot Room Compression Stuff Sack Insulated Collar with Easy Access Cord - Engineered to Close Without Velcro Keeps Warm Air Trapped in Your Bag