Remember, the reversed lens doesn't have to be
from the current camera system as it is being mounted by its filter thread.

Canon EOS Reversing Rings An electronically coupled reversing ring from Novoflex giving auto functions

Canon FD Reversing Rings Reverse mount Canon FD lenses onto camera body, extension tubes, or bellows

Contax / Yashica Reversing Rings Reverse mount Contax/Yashica lenses onto camera body, extension tubes, or bellows

M42 Reversing Rings Reverse mount M42 screw lenses onto camera body, extension tubes, or bellows

Minolta AF/Sony Alpha Reversing Rings Reverse mount Minolta AF/Sony Alpha lenses onto camera body, extension tubes, or bellows

Minolta MD Reversing Rings Reverse mount Minolta MD lenses onto camera body, extension tubes, or bellows

Nikon Reversing Rings Reverse mount Nikon lenses onto camera body, extension tubes, or bellows

Olympus OM Reversing Rings Reverse mount Olympus OM lenses onto camera body, extension tubes, or bellows

Pentax K Reversing Rings Reverse mount Pentax K lenses onto camera body, extension tubes, or bellows

Reversing Ring Inserts For T-Mounts Converts a T-Mount into a reversing ring