SUPON Metal Auto Focus AF Macro Extension Tube/Ring for Canon 70D 550D 600D T2i Black This is a quality Phootlex Auto Focus Extension Tube set which includes 3 tubes of different lengths 13mm, 21mm, and 31 mm - which can be used individually or in any combination to obtain the desired magnification. These extension tubes are designed with all the circuitry and mechanical coupling to maintain auto focus and TTL auto exposure with Canon lenses, given there is enough light to activate the cameras AF system properly. Auto-Focus