Mega Spring warehouses the largest inventory of high-grade, straight, cylindrically-shaped compression springs in the world. A compression spring is an open-coil helical spring that offers resistance to a compressive force applied axially. They are usually coiled at a constant diameter, though they can be coiled in other needed forms such as conical, concave (barrel), convex (hourglass), or various combinations of these. Compression springs are used to resist force and/or store energy, depending upon the application. All Century compression springs are fabricated from round wire.