M42 to M42 Mount Lens Adjustable Focusing Helicoid Macro Tube Adapter - 17mm to 31mm The all-metal adapter is designed to fit the lens securely and can be easily removed when not needed. This tube is useful for lenses without a focusing ring and can also be used as a macro extension tube. There are no electronic components in the adapter; aperture and focusing must be manually controlled. Material: Aluminum alloy Made of anodized aluminum with a black finish and high-quality construction. The length of this helicoid tube ranges from 17mm (minimum) to 31mm (maximum), providing a total of 14mm of movement for precise lens focusing. Compatible with M42 screw mount lenses, including Carl Zeiss and Pentax 42mm screw mount lenses, as well as enlarger lenses. This helicoid tube is ideal for lenses without a focus ring, offering fine focus control for macro photography. The focusing helicoid tube features a 42mm front mount and a standard 42mm rear mount, constructed from lightweight alloy. It can be used as a macro extension tube. Automatic diaphragm and autofocus functions will not operate when using this adapter. Manual focusing with manual exposure mode is supported. Compatible With: M42 Lens and M42 Mount Camera Package Includes: 1 x M42 to M42 Mount Lens Adjustable Focusing Helicoid Macro Tube Adapter - 17mm to 31mm Note: The package includes only the items listed above. Other accessories are not included. Note: Lighting and display differences may cause slight color variations between the product image and the actual item. Measurement error is +/- 1-3cm.