Focal Reducer Mount Adapter for Nikon G Bayonet Lens to Sony NEX Mount 5 6 7 Camera Focal Reducer Speed Booster Adapter Lens Turbo (NIKON G-NEX) for NIKON G / AI / AI-S / NON-AI to Sony NEX5 6 7 Made of metal structure and excellent optical glass with multi-coated Effectively increases the maximum aperture of the lens by 1 stop, in other words, under the same aperture, you can use faster shutter speed (by 1 stop)