Mattress coil

Mattress coils, also known as mattress springs, are coil springs used in a mattress. Coils are primarily used in the core (support layer) of innerspring mattresses, which is their original use. In recent years, small "micro-coils" are being used in the upholstery (comfort layer) of mattresses, primarily with a coil core ("coil-on-coil" construction), but sometimes with other core types.

Mattress coils were introduced in the mid-late 19th century, and remain popular in the 21st century, particularly in the United States.