Fotodiox Pro Auto Macro Extension Tube, 31mm Section - for Canon EOS EF/EF-s Lenses for Extreme Close-up Any combination of tubes can be used for various reproduction ratios No optical insert - maintains lens optical quality Maintains the electronic functions of the lens, including auto-focus and auto-exposure Three extension tube sections available: 13mm, 21mm, and 31mm 24 Month Manufacturer Warranty