The patented lock cylinder has a novel cylinder structure with an ‘anti-bumping’ function, pick resistance, and drill resistance. The lock cylinder can be unlocked only when the key combination matches the combination of the lock cylinder. One key can unlock a dozen lock cylinders as long as they have the same combination as the key. Both key and lock cylinder are equipped with an instant combination-reset function so that safety is guaranteed. This product does away with the need to carry around a bunch of keys.