This is a Sigma USB Dock UD-01 For Canon. 

By connecting an Art, Contemporary, or Sports lens to a computer with the Sigma USB dock photographers can update the lens firmware and adjust focus position and other parameters. Exclusive Sigma Optimization Pro software makes customization easy. It is possible to select the autofocus speed and adjust the focus limiter and Optical Stabilizer (OS) function. This dock comes in original packaging with an instruction manual and cap. Cosmetically there is minimal wear from use. 

WE SHIP IN 1 BUSINESS DAY and we package professionally and will combine to save on shipping costs. We are also interested in BUYING your photographic equipment as well. We are Camera Exchange in Waterford Michigan.

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