This kit will increase the locking tension of swing-out cylinders in double-action revolvers chambered for heavy-recoiling calibers. The kit will also allow the revolver crane (holding the cylinder) to be better aligned in the frame, leading to more precise cylinder alignment with the barrel. Gunsmithing, including firearm machining and drilling, is required. This is intended for use on custom-made revolvers and will not work with stock applications. Kit comes with 20 crane balls, 20 springs and an installation punch.