Kenko Extension tubes for Canon, mint condition with box – €80
I’ve used these in two scenarios, one is on zoom like the 24-70 and 70-200 for doing ring shots at weddings, a fraction of the cost and weight of a dedicated macro lens.
The second is on a super tele lens like the 500mm to overcome the minimum focus distance to photograph small birds.
More information on the following site http://www.the-digital-picture.com/Reviews/Kenko-Extension-Tube-Set-Review.aspx
They are for the Canon mount, I’ve used them with a Sigma 180mm macro lens when I had Canon gear, but this is the only combination I can comment on. Best I can suggest is test them before buying if we have agreed a sale and you can meet around Cork.