New 49mm Olympus OM mount lens reversing ring for extreme macro close up photography. With this ring attached to a lens mounted in reverse, you will be able to achieve greater than 1:1 magnification, depending on the lens you are using. The threads are 49mm so the front filter threads of the lens you want to mount in the reverse position needs to have 49mm threads. (If you are unsure of the filter thread size, it is usually inscribed on the back of the lens cap). The lens does not even have to be an Olympus brand or have an Olympus mount , as this ring provides the correct mount for Olympus OM mount cameras.