Round wire springs, also known as helical springs, are a type of compression springs and are the most common type of springs. They have a circular cross section and are mainly used for rebound, shock absorption, and thrust. When the spring is a linear spring, the spring load (N) = constant (N/mm) x compression (mm). The materials include piano steel wire (SWP) and stainless steel wire (SUS304), which have different heat resistance and load levels. The specifications include both ends ground and non-ground.