Polaroid? Macro Extension Tube Kit C-AF Digital (13mm, 21mm, 31mm) for Canon EF
This is a nice macro extension tube kit for Canon EF that allows you to focus much closer while still maintaining full integration between your camera and lens (including autofocus!). I believe they are made by Polaroid but I'm not positive.
The 13mm tube, 21mm tube, and 31mm tube are included.
They are in excellent condition with light wear and work perfectly.