They've been sold by the millions to colleges and convenience stores around the country. But do they really work?
They're paper coasters on which to place drinks. And the makers of the coasters say they are 95 percent accurate in testing for "date-rape" drugs.
The coasters have spots that are supposed to turn dark blue in about 30 seconds if a splash of alcohol contains the drugs.
But some experts say they don't really work -- and that they could lead to more harm than good, by providing a false sense of security.
Tests at one police lab showed the coasters didn't react clearly to drinks spiked with the date-rape drug known as GHB.
And the co-inventor of the coasters acknowledged that they only identify two of the many date-rape drugs out on the streets.
The head of the company that makes them said they're like condoms -- they might not be 100 percent effective, but they're a good prevention tool.