[martinml]

You're probably thinking of "tag". The "ref" parameter doesn't have anything to do with Amazon's affiliate program (which is what I understand you're talking about).

[mattcwilson]

Yup. zgbs is the correlator for "Best Sellers", and 3151491 seems to be thumb drives.

http://www.amazon.com/Best-Sellers-Electronics-USB-Flash-Dri...