Why 2 lots please is one superior to the otherYup. Canon EF12 and EF25
or kenko pro's? they are just empty space anyway.
Cheers PaulOne is 12mm long and one is 25. You can also use both together to get 37mm. Depends how close you want to get, which tube you use.
I got rid of my Kenkos as they didn't feel mechanically strong enough to hang a 1-series body off a 500mm lens but they do the job otherwise.