M52 to M42 Lens Helicoid Adapter 17-31mm Adjustable Focusing 42mm Screw Mount Camera Macro Extension Tube Ring 
Description:
1. This focusing helicoid tube is made with M52 front mount and standard M42 rear mount and light-weight alloy. It is useful for those lenses without focus ring, offers fine focus control for macro photography.
2. Mounting Extension Tube in between the camera body and l.ens will create more distance between the l.ens and film plane. By moving the l.ens further away from the film or digital camera sensor, the l.ens is forced to focus much closer than normal. The greater the length of the extension tube, the closer the l.ens can focus.
3.Use this tube with your normal l.ens and you will get the quality, which is as good as the original l.ens and the size, sharpness and versatility is perfect for the macro and close-up pictures.

Specification:
Material: Metal
Length: 17mm/0.67in (minimum) to 31mm/1.2in (maximum), provides total moving distance 14mm/0.5in 
Compatibility: M52 is used for 42mm lens and camera mounting screws
Product size: 65*65*20mm/2.56*2.56*0.8in
Product weight: 64g
Packing size: 75*75*30mm/2.95*2.95*1.2in
Package weight: 73g

Note:
There is no electronic connection between the body and the lens Auto-focus function cannot operate. When using the extension ring with a DSLR/ SLR, the camera should be set in the 'M' mode.
Due to the different monitor and light effect, the actual color of the item might be slightly different from the color showed on the pictures. Thank you!
Please allow 1-2cm measuring deviation due to manual measurement.