In 1995 I bought a used EF 300 4L USM in mint condition for $600.
Unfortunately, the "Tripod Mount Ring A" was missing. The only one listed in my
dealer's catalog was a replacement Tripod Mount Ring for the old EF 80-200
2.8L. I tried it on my EF 300 4L USM and it fit perfectly, although it is black and
not white.
The same "Tripod Mount Ring A" is used for the EF 200 2.8L USM, EF 200 2.8L
USM II, EF 70-200 4L USM and the EF 300 4L USM. The only difference is that
some are black and some are white. The white one costs more, I don't know why,
but I bought the white one for my new EF 70-200 4L USM. It is exactly the same
size as my old black one except for being white and costing $66 more!
http://www02.bhphotovideo.com/default.sph/
FrameWork.class?FNC=CatalogActivator__Acatalog_html___CatID=277___SID=
EB8EC827720
-- Puppy Face (doggieface@aol.com), January 11, 2002.