foam cores and latex cores have long been popular. These make up a much larger proportion of the mattresses sold in the continent. Construction A conventional mattress consists of two primary sections – a core or "support layer" and the upholstery or "comfort layer" – wrapped in a thick fabric called the ticking. Upholstery layers cover the mattress and provide cushioning and comfort. The upholstery layer consists of three parts: the insulator, the middle upholstery, and the quilt. Sizes Mattresses are typically made to conform to bed sizing standards that vary by market. The size of mattress varies between national standards in width and height and depth. Many countries use non-numeric labels such as "King", "Queen", "Double", "Full" or "Single" to represent these dimensions. Mattress topper A mattress topper is a thin mattress, usually thick. Stand-alone mattresses of this size exist (see futon and Bed base#Floor beds; traditional European beds were made of a stack of mattresses of this size). But "mattress topper"s are usually sold for use on top of boxsprings (secured with straps or elasticated cloth corners). They are used to extend the life of the more-expensive boxspring, make a bed warmer or cooler (with airflow, or heat-conductive materials), make a firm bed softer, and for travel and dorms, as they are portable, especially if they are low-density. Like a mattress protector/mattress pad/mattress cover (a thin, generally unpadded layer not designed to improve comfort), mattress toppers can be used to protect the mattress from the sleeper or vice versa. Some mattress toppers are machine-washable; covers and fillings are made from a range of materials. Types Tick mattress A tick mattress is a bag made of ticking (a type of cloth), filled with some suitable material. A paillasse or a featherbed is a tick mattress, as are most futons. They are simply constructed and were traditionally homemade. Because they are fairly thin and light, they are layered to form a bed. Innerspring Innerspring mattresses commonly consist of just the spring core, and the top and bottom upholstery layers. Core The core of the mattress supports the sleeper's body. Modern spring mattress cores, often called "innersprings" are made up of steel coil springs, or "coils". The gauge of the coils is one factor which determines firmness and support. Coils are measured in quarter increments. The lower the number, the thicker the spring. In general, higher-quality mattress coils have a 14-gauge