Kaavie -The Premium Aluminum Mount Version (Rugged and Lightweight, Best Option Extended Goal) - Set Automatic Extensions Ring for Canon Eos Ef / Af - * 3 Rooms: 13 Mm, 21 Mm, 31 Mm * Bayonet - Canon EOS Canon EOS 1d C, 1d X, 1d Mark I-iv, I-1ds 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 bayonet Transmits all lens data Front and rear cap