Description: Made of Anodized Aluminum in Black finish with high quality. You can use M42 screw mount lenses, such as Carl Zeiss or Pentax 42mm screw mount lenses, and even enlarger lenses. The length of this Helicoid tube 36mm (min) to 90mm (max), it offers a total of 54mm movement distance for lens focusing. Instruction, mount the Helicoid tube to your lens, and then the combination of lens and Helicoid tube to the camera. This Helicoid tube is useful for those lenses without focus ring. It could be used as Macro barrel and offers fine focus control for macro photography. Specification: Size: 6X6X4CM Color: Black Suitable For: Lens: M42 Mount Lenses Cameras: M42 Mount Cameras Package Includes: 1 Piece M42 Focusing Helicoid Adapter Note: Please allow slightly 0-1cm difference due to manual measurement. Colors can appear different depending on light and how the listing is viewed. Thanks for your understanding and attention. Wish you a pleasant shopping experience!