The Leupold 49974 is a product built with a precision machined steel construction. Its main feature is the ability to remove and reattach a scope, while still being able to return to within half an inch of the original point of impact on the target. When you turn the lever forward, an eccentric on the lever shaft will engage the base of the ring. This action pulls the ring down and forward on the base, effectively locking it solidly into its \"zero\" position. Note that the Leupold 49974 is also available in Extension Rings.