Replacement recoil spring. Some fitting may be required.
Recoil springs fit over a pistol's guide rod and control how the pistol's slide functions. In general, heavy loads need heavy springs and lighter loads need lighter springs.
There is no hard and fast rule as to how much "spring" a pistol needs. Too light a spring and the pistol opens and closes early and hard, increasing felt recoil and battering the frame. Too heavy a spring and the slide is hard to open and may not cycle completely, jamming the pistol.
Factory Beretta 92 recoil spring is 13 lbs for standard ball ammunition. Shooters who are using +P ammunition or self- defense ammunition will likely need heavier recoil springs. Every recoil spring package contains a free extra power firing pin spring.