When choosing between the many types of sleeping bags, the three main factors to consider are shape, shell material and filling material for insulation. Shape affects the bags heat trapping efficiency, bulkiness, and sleeping space. Shell Material affects the sleeping bags resistance to wind and water. Fill Material affects the bags temperature rating, weight, bulkiness, packed size, drying rate, durability and cost. You should not get a bag that’s roomier than you need, because having a lot of extra space to heat up can leave your body feeling colder.
Different types of shell materials can be used in sleeping bags. Microfiber is a tightly woven polyester or nylon. It is not as water-resistant as coatings or membranes, but is lighter and cheaper. Dryloft is windproof and highly water-resistant.