Rock is fed into a large opening at the top of the cone crusher where it is squeezed between the mantle and the cone. As the size of the rock decreases, pieces fall into lower levels of the crusher where they continue to be worn and broken down further. Once small enough, the fragments of rock exit through a narrow opening at the base of the machine. Cone crushers manipulate rock between a fixed cone and the movable cone (the central shaft). The width of the exit opening is adjustable through ascending and descending the fixed cone which allows the rock to be crushed to a variety of sizes.