M42 To M42 Helicoid With Adjustable Focal Point 17-31mm Tube Black : This helicoidal focal length is made with a standard M42 mount. You can use M42 screw mount lenses, such as lenses or 42mm screw mount lenses, or even magnifying lenses. Length of this helicoid tube from 17 mm (min) to 31 mm (max. ), carefully at a distance of 14 mm of movement for focusing the lens. Easy installation: mount the helicoid tube on the lens, then connect the lens and the helicoid tube to the aparatu.Ta helicoidal is used for lenses without focus ring. It can be used barrel and provides precise focus control for macro photography, it will be better, you work it with adapter. Specification: Material: Aluminum Alloy Black Size: 5,6 x 2cm It can be done: Lens: M42 mount lenses Cameras: camera with M42 mount Settings: Determination of red markings and lens flange. Turn the adapter in the direction of movement of this clock until you hear verification. original language or AV. methods: To see the adapter, unscrew the mounting pin and turn the adapter in the direction that is compatible with the clock. contains: 1 M42-M42 (17-31mm) excellent helicoidal adapter for focusing