I bought a lens used and I needed a tight-fitting lens cap for it that wouldn't constantly fall off. There are a zillion of these cheap telephoto lenses that are 500-1000mm f/8 under different names, but they housing seems the same Ultimaxx, Vivitar, Opteka, Beroflex, that all seem to have the same housing. This should fit most lens with an OD barrel diameter of 70mm. The inside is tapered by .25mm which creates a very snug fit without damaging it. I added some little grip ridges around the outside to make it easy to remove and install.