A sleeping bag is an insulated bag used for warmth when backpacking, camping or sleeping outdoors. Sleeping bags are filled with goose down or synthetic insulation. Goose down is more expensive but provides a better weight to warmth ratio. Goose down bags should be stored uncompressed to prevent compression and or damage to the down. In cold weather, a sleeping pad may also be used to prevent loss of warmth to the cold ground and for comfort.
Sleeping bags typically zip on up on either side and may include a hood for warmth. Sleeping bags usually come in a mummy shape, contoured shape or rectangular shape.
A lighter and more versatile evolution of a sleeping bag is called a top quilt.