M42 to M42 Mount Lens Adjustable Focusing Helicoid Macro Tube Adapter 25mm to 55mm Allmetal macro tube adapter with M42 threads on both ends, designed to fit M42 screwmount lenses and M42compatible camera bodies Adjustable focusing extension from 25 mm to 55 mm via a precision helicoid, enabling closer focus and true macro results Durable, allmetal construction provides rigid alignment and longterm reliability; threads are designed for secure attachment and easy removal when not in use Simple, tool installation: screw onto M42 threads on the lens and camera body; no electronics or additional adapters required Smooth, controllable manual focus: rotating the helicoid delivers precise, repeatable focus adjustments for closeup photography Compatibility: suitable for lenses and bodies that use M42 screw threads; maintains standard M42 mounting without altering other specifications Use scenarios Closeup macro photography of flowers, insects, and small subjects to reveal texture and detail Jewelry or product photography requiring close focusing and shallow depth of field Educational or hobby applications where precise macro shots of small components are needed Notes Keeps the lens securely mounted while in use, and can be removed easily when macro work is not required