A compression spring is an open-coil helical spring that offers resistance to a compressive force applied axially. Compression springs are usually coiled as a constant diameter-cylinder. Other common forms of compression springs--such as conical, concave, (barrel,) convex (hourglass), or various combinations of these--are used as required by the application. While square, rectangular, or special-section wire may have to be specified, round wire is predominant in compression springs because it is readily available and adaptable to standard coiler tooling. Compression springs should be stress-relieved to remove residual forming stresses produced by the coiling operation. Kato Spring can produce compression springs with wire diameters of .005" to .125" in a variety of materials and specifications.