The extension tubes are essential to make Macrophotography, or to make close-ups with small telephoto lenses which closest focusing distance is too far (for example the photography of my Praktica BC-1 on this site: EOS 400D + M42 adapter ring + Telemar 22 5.6/200mm with the longest of these 3 rings).Until then I used an equivalent set of extension tubes, but Japanese made, with coupling for automatic diaphragm.