The U.S. Navy ordered 40,000 Mk285 40mm shells, each equipped with a time fuze. Normally only used in larger artillery shells, a time fuze in 40mm grenades makes it easier to get at enemy troops on roof tops or behind walls. These shells, which cost $213 each, must be fired from one of the new 40mm automatic grenade launchers, like the Mk47. This weapon is replacing the Mk19, and has the electronic sighting and arming system which enables the gunner to determine the distance of the target (with a laser range finder), then push a button to have the weapon electronically program each shell, just before it is fired, for the number of seconds until the shell will explode, at the proper range from the gun, and above the enemy troops. If the time fuze does not work, the shell explodes when it hits something. The first troops to get these special shells, and weapons like the 96 pound Mk47, are special operations troops, like navy SEALs.