Meike MK-S-AF1-A Macro Auto Focus Extension tube Ring AF for Sony Alpha A57 A77 A200 A300 A330 A350 A500 A550 A850 A900 MK-S-AF1-A Standard version extension tube set Professional extension tube set, design for Sony  DSLR. Support AF(Auto-Focus), AF Motor Protection: while using 3 rings together, we suggest you to use manual focus for it's a little bit difficult to auto-focus with 3 rings together, and also protecting your lens motor. ConfigurationEngineering plastics material + metal bayonet, perfect match with Sony  DSLR camera and lens. Length:12mm+20mm+36mm, seven kinds of combinations, seven kinds of magnifications