M42 to M42 Lens Adjustable Focusing Helicoid Macro Tube Adapter-17mm to 31mm black
Made of Anodized Aluminum in Black finish with high strength.
The length of this Helicoid tube is 17mm (min) to 31mm (max),it offers a total of 14mm movement distance for the lens focusing.
You can use M42 screw mount lenses, such as Carl Zeiss or Pentax 42mm screw mount lenses, and even enlarger lenses.
This Helicoid tube is useful for those lenses without focus ring, Tube offers fine focus control for macro photography.