Compression springs are open-coiled, helical springs that store mechanical energy. They shorten under compressive force to absorb impact, apply pressure to surfaces, or protect against the affects of shock. They're common in applications such as push-button controls, pens, appliances, and tools. Die springs are a type of compression spring that have a rectangular wire shape. They are stronger than compression springs and ideal for high-load or extreme temperature applications with limited space like brakes, clutches, and heavy machinery.