M42-M39 12mm-19mm Macro Focus Lens Helicoid Adapter For Fastening Professional Parts : Handheld lens adapter with helicoidal macro tube for screw-on lens of screw-on camera body M39 39 mm The macro function provides a focusing helicoid that increases the distance of the lens to the sensor, allowing closer focusing than normal allows the lens This means that you can get macro performance without having to switch to a specialized lens and you will retain all the normal advantages of your optics when the macro function is not in use This allows you to take close-ups/macro full stretch more easily Of course, you can focus on infinity when it is closed Length of this 12mm-19mm helicoid tube, (7mm motion distance for focusing) Specification: Lens Compatibility: M42 to M39 Length: 12mm-19mm (movement distance 7mm for focusing) Sharpness: manually Material: aluminum alloy; contains: 1 for lens