Nikon BR-2A 52mm Lens Reversing Ring

here is some info
Description

The BR-2A enables you to mount a 52mm front thread lens (eg. Nikkor 50mm lens) in reverse on the Nikon SLR / DSLR or PB-6/5/4. Nikon BR-2A changes your lens into a macro lens with just a fraction of the cost that you need to spend on a macro lens.

Magnification Ratio with different lenses

* Nikkor AF 20mm f2.8 : 3.4X
* Nikkor AF 24mm f2.8 : 2.5X
* Nikkor AF 28mm f2.8 : 2.0X
* Nikkor AF 35mm f2 : 1.4X
* Nikkor AF 50mm f1.4 : 1/1.1X
* Nikkor AF 50mm f1.8 : 1/2X
* Micro Nikkor AF 60mm f2.8 : 1/1.2X