This tungsten hammer weight for the FX Maverick, Wildcat MKIII, Dreamline and Crown air rifles replaces the original hammer. An upgrade that causes the valve to be opened for a prolonged period of time, which releases more pressurized air to thrust a projectile out of the barrel.
This is possible because of the material density of tungsten, which is 1.7x that of steel and thus increases the weight, which causes the longer valve release. A handy improvement very much suited for use with heavier slugs, which need more thrusting force.