Canon Auto Focus Extension - Description:
Canon EF25 Extension tube is the two Extension tubes, in the same 12mm and 25mm lengths as previously available, have been redesigned to accommodate the Canon EF-S mount lenses and its extended rear elements. They're perfectly compatible with all previous Canon EF and Canon TS-E lenses, and will work with any Canon EOS film or Canon EOS Digital SLR.
Note that exposure compensation is often required with cameras other than the EOS-1 Series.

Features of Canon EF25 II Extension Tube
Version II extension tubes are the only tubes compatible with Canon EF-S 18-55mm lens
White index mount is for EF-S lenses ; Red dot is for use with Canon EF and Canon TS-E lenses
Canon 25mm Canon EF 25 II Tube provides greater close-focus capability, especially with lenses 50mm & up
Extension tubes work well with telephotos to allow closer focus tham normally possible
Manual focusing is recommended, and with zoom lenses, focus after zooming is completed