The silver LH-X100 Lens Hood with Adapter Ring from Fuji is for the X100 camera. This metal adapter ring replaces the lens ring that comes with the camera and bayonet mounts with the lens hood. In addition to bayoneting with the hood, it can also be used for mounting 49mm filters.
The metal lens hood helps minimize flare by providing shade to the optic. It also guards the lens against incidental bumps and abrasions. It also contains a slit that prevents it from blocking the viewfinder.