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 removed easily when not needed. This tube is useful for lenses without a focusing ring and can be used as a macro extension tube. There are no electronic elements in the adapter. Aperture and focusing must be manually controlled. Material: Aluminum alloy. Made of anodized aluminum in black with high quality. The length of this helicoid tube ranges from 17mm (min) to 31mm (max), offering a total of 14mm movement distance for lens focusing. You can use M42 screw mount lenses, such as 42mm screw mount lenses, and even enlarger lenses. This helicoid tube is useful for lenses without a focus ring. The tube offers fine focus control for macro photography. The focusing helicoid tube is made with a 42mm front mount and standard 42mm rear mount, and is constructed from lightweight alloy. It can be used as a macro barrel. Automatic diaphragm and auto-focusing will not operate correctly while using this adapter. Manual focusing with manual metering is compatible with the adapter. Compatible With: M42 Lens & Camera Package Includes: 1 x M42 to M42 Mount Lens Adjustable Focusing Helicoid Macro Tube Adapter - 17mm to 31mm Only the above package content is included; other products are not included. Note: Light and different displays may cause the color of the item in the picture to appear slightly different from the real thing. The measurement allows an error of +/- 1-3cm.