K&F Concept Lens Mount Adapter for M42 42MM Thread Mount Lens to Pentax PK Lens Camera Body Allows to use M42 mount Camera Lens to Pentax PK lens camera. High quality provides great protection and shock absorption for your lenses, water-resistant. Made of brass and aluminum(not plastic), high quality and compact. The adapters are precision made to insure the perfect fit. Please note: Infinity focus positionthe position of the infinity mark of the telephoto lens or super telephoto lens is shifted slightly to the positive side to enable focus adjustment even when focus shift is caused due to temperature changes.The shift range is denoted by an L-shaped line, Be sure to check the focus through the viewfinder even when you shoot at infinity.