The concept of layering for different conditions is nothing new to outdoor enthusiasts. For example, you wear one garment next to your skin and then add layers to obtain the ideal temperature and moisture management system. Sleeping bags arent much different and we want you to think that way too. Combine a sleeping pad, any sleeping bag and a Big Agnes over bag to create a versatile year-round system that you can pick from based on trip and temperature needs. Benefits of layering include added warmth, versatility, moisture transfer, value and comfort. Synthetic over bags are ideal when moisture is a concern as they insulate when wet and protect the inner bag while down over bags perform better in dry conditions. Mummy shaped bags, such as the Horse Thief, can be used as a liner bag or make a great over bag for the minimalist.