This is telephoto accessory that fits on the front of your 2.8F (and maybe others with size bay III filter mount) Rolleiflex TLR with size bay III and turns it into a 116mm lens. The lenses are made by Carl Zeiss. These were produced originally for the 75mm f/3.5 TLR's however they made adapters for the 80mm f/2.8 versions. You can see on the back that this also has the bayonet II size tabs on the inside of the size III adapter ring. The front of the taking lens will accept a screw thread filter. Overall in very nice condition with excellent glass.