This focusing helicoid tube is made of good aluminium alloy, sturdy and durable, equipped with standard M42 mount.
The length of this helicoid tube is adjustable, it offers a distance for lens focusing adjustment, easy to use.
This helicoid tube is useful for those lenses without focus ring.
It will be better when you use it with filter adapter together.
It can be used as macro barrel and offers fine focus control for macro photography.