This is an LM mount adapter. It's an adapter for attaching Leica screw (L39) mount lenses to M bodies. The rangefinder frames are aligned. It's a no-brand product, but I've had no problems with focus using it on my Leica M2. It's designed to fit the 50-75mm and 35-135mm bright frames. Set of 2 metal M39-L(M) mount adapters. - Model: M39-L(M) (50-75) - Model: M39-L(M) (35-135) - Design: Metal Thank you for looking.