I went on using it with the EOS 5D, before I bought the 24-85.
Christophe has bought an EF 24-70L f/2.8 USM and an EF 70-200L f/2.8 IS USM for using on his EOS 40D and 5D, so he doesn't use the 75-300 and let it to me.
The 80-200 is a little limited for short distances, this ring allowed me to approach a little more, among others for the photos of this site, before I bought the 100mm Macro Takumar.
Alain has no Canon camera, he found this zoom, useless for him, and gave it to me.
Came with the EF-M retrieved in waste disposal in July 2016. Motor of the autofocus seized, dust inside. I rarely will have the opportunity to use it.