The CRC .55mm Pro-Tapered Side Spring Fits CRC and most link cars using the tapered cone springs. CRC's side springs are made from unpainted music wire which is known for its high tensile strength and high elastic limit. Music wire can withstand high stresses under repeated loadings, and will continue to perform well under many normal cyclic applications. Pro-Taper springs are available in .45mm, .50mm, .55 mm and .60mm. They fit the CRC spring holders as well as many other manufacturers.