They work very well for something so small. A couple of months ago, I
started setting off the theft prevention alarms in just about every
store that had them. Walmart, Target, Kohls, Mervyns - you name it, I
set off their alarm. Started to be annoying when I would be walking
out of the store with nothing, and the security people would be
looking at me like they were thinking whether to ask if I had anything
in my pockets.

Took me a while to figure out what was setting off the alarms. I had
bought a new leather checkbook cover recently. Hidden in bottom of one
of the credit card slots was an RFID tag, paper-thin, and about 1 inch
square. Took it out and no more dirty looks from the "loss prevention
specialists".

Jerry