Nikon M2 27,5mm PRE AI Tubo Prolunga Obiettivo per Macro 1 a 1 Lavoro Ecc++++
The M2 was the predecessor to the PN-1 extension tube. The M2 doesn't have the stop down connector, so it works purely as an extension tube to give 1:1 reproduction when used with a Nikkor 55mm f/2.8 or 55mm f/3.5 Micro Nikkor.