52mm-52mm Male to Male Thread M-M Macro Photography Lens Coupling Ring for Mounting Two (2) Lenses Face to Face Metal This ring is used for extreme macro close up photography. Both sides are threaded with 52mm male threads. It is suitable for manual and auto focus lenses. The lens mounted in the reverse position must be focused manually but this lens can be either manual or auto focus. Any brand or type of lens can be used as long as it has 52mm threads.