Modify lens purpose,can not focusing infinitely when used directly. Fine finishing! Install,remove and operate lens smoothly! Although the lens will fit physically,automatic diaphragm,auto-focusing,or any other functions will not operate correctly while using this adapter. With this adapter,you can Modify m42 mount large format or enlarging lens for Camera. M42 mount large format or enlarging lens with focusing tube and this modify lens adapter,use for camera.