Police officers searching a suspect in Leeds have recovered what was initially thought to be black credit card - before realising it transformed into a knife.
West Yorkshire Police's Roads Policing Unit tweeted a picture of the hidden blade after discovering it in the possession of a detainee.
Officers who successfully completed a search of an arrested male labelled the device 'a credit card knife' - which could do "serious harm".
However, a quick search of Amazon reveals that the gadgets are sold legally on the internet giant's US site.
Although they do not ship to the UK, the Holtzman's credit card knives are priced at just under ten dollars and are marketed as the 'best wallet knife' to be used in outdoor survival situations.