In article <33D577B0.74A2@us.gases.boc.NOSPAM.com>,
sean.hennessey@us.gases.boc.NOSPAM.com says...

>i am looking for a piece of hardware i am told is called an "m" ring.
>i'll describe what i'm looking for, and hopefully someone will tell me
>the correct name. the equipment is supposed to have come with the old
>macro lens to give them a true 1:1. i need one that is ai'd. the camera
>i have is a nikon 8008s. the lens i need it for is a micro-nikkor 55mm.
>the lens has four rings of numbers on it. ft, meters, and what looks
>like two sets of ratio numbers. the first set is unlabeled. it starts
>at 1:10 and goes to 1:2. the second set is labeled pk and goes from 2 to
>1. maybe the pk means it needs a pk ring? if so which one. any and all
>advice is greatly appreciated.

You want a PK-13, the AI version of the "M" ring for the Nikkor 55mm
macro (BTW, I have a couple of "M" rings, real cheap...;-). BTW, if
you can stop down to about f8 or so (f16 effective), the TC200/1 or
Vivitar Macro 2X converters will also give you 1:1 (or higher, with
the Vivitar...).
Hope This Helps
(David Ruether - http://www.fcinet.com/ruether )