The Big Agnes Summit Park 15 Sleeping Bag follows the tradition of Big Agnes Park Series Sleeping Bags but instead of using Polarguard Delta, the Summit Park uses 650 Goose Down insulation. By using Goose Down insulation in the Big Agnes Summit Park, you have the best of both worlds in room and weight. The Summit Park is not only geared for car camping but lightweight enough to work with backpacking adventures as well.