In camping, a ground pad, sleeping pad, thermal pad, sleeping mat, or roll mat is lightweight pad, common among hikers, backpackers and budget travelers, often used in conjunction with a sleeping bag. Its purpose is to provide padding and thermal insulation. All types currently available use air as their primary form of insulation.
In its simplest form a sleeping pad consists of a foam-like material that is about half a centimeter thick (about a quarter of an inch). The dimensions of the pad are usually about the same length as a sleeping bag and a little wider. Slight variations in design can be found, such as rippling in the foam, but these do not significantly affect the pad's thermal properties.