Compression Springs provide resistance to external load pressure. Compression springs are generally coiled metal wires with equal pitches and fixed wire diameters. Compression springs use multiple open coils to provide resistance to external load (such as gravity pressing down on a wheel, or body pressing on a mattress). That is, they push back to resist external pressure. Compression springs are generally coiled metal wires with equal pitches and fixed wire diameters. In addition, there are also conical compression springs, or a combination of conical and linear springs. According to different application areas, compression springs can be used to resist pressure and/or store energy. Round wire is the most commonly used compression spring, but there are also compression springs made of square, rectangular and special shaped wires.