1This focusing helicoid tube is made of good metal, sturdy and durable, equipped with standard M42 mount 2The length of this helicoid tube is adjustable, it offers a distance for lens focusing adjustment, easy to use 3This helicoid tube is useful for those lenses without focus ring 4It could be used as macro barrel and offers fine focus control for macro photography 5It will be better when you use it with filter adapter togetherFeature:This focusing helicoid tube is made of good metal, sturdy and durable, equipped with standard M42 mount. The length of this helicoid tube is adjustable, it offers a distancefor lens focusing adjustment, easy to use. This helicoid tube is useful for those lenses without focus ring. It could be used as macro barrel and offers fine focus control for macro photography. It will be better when you use it with filter adapter together.Specification:Material: Aluminium Alloy Color: Black Options(Adjusting Length): 12-17mm; 17-31mm; 25-55mm; 36-90mm Size/Diameter: Approx. 5.8cm / 2.28inch Weight: Approx. 57-102g Package list:1 x Focusing Helicoid Adapter