Kaavie - The Finest Set automatic extensions ring for Canon EOS EF / AF 3 rooms: 13 mm, 21 mm, 31 mm Bayonet - for Canon EOS Canon EOS 1D C, 1D X, 1D Mark I-IV, 1Ds I-Mark III, 5D Mark I-III, 6D 7D 60D 50D 40D 30D 20D 10D 1100D 1000D 650D 600D 550D 500D 3 rings - 13 mm, 21 mm, 31 mm, Material: copper and ABS (acrylonitrile-butadiene-styrene) Combined - 7 possible combinations Compatible with EF, EF-S, AF Canon EOS Transmits all lens data Front and rear cap