Have you ever bought a high-end watch, a designer bag, or a classic hockey jersey, only to find out later it's actually a knock off.
That kind of counterfeiting is a huge industry around the world, especially online, and it's costing the economy millions of dollars.
Last year, the RCMP said it seized $78 million worth of bogus goods - including golf clubs, team jerseys, toys and action figures, watches, Viagara and Cialis pills, cosmetics, heart pills, and cellphones.
"These products not only rob legitimate manufacturers and the Canadian economy from revenues, but often finance organized criminals and place lives in danger," said Brian Isaac, chair of the Canadian Anti-Counterfeiting Network.
Well now, researchers in Sweden say they've developed a new way to fight clothing counterfeiting which manufacturers could start using right away.
It's a unique type of thread that is said to be invisible to the naked eye, but can be seen under specialized light.
The researchers say the thread has unique optical properties so manufacturers can create a signature pattern in their clothes - making it easier to tell the real thing from the knock offs.
The thread was developed at Chalmers University in Sweden, by Christian Müller who specializes in chemical engineering and polymer technology.
Müller created the thread from polyethylene and a polymer used in clothing dye.
He says it can be made using synthetic textile such as nylon, and the dye molecule can be bonded to natural fibres such as wool and silk.
And Müller says fashion houses and manufacturers can create their own unique combinations and patterns, that can only be seen under polarized light.
According to a National Post report, the counterfeit black market in Canada is worth some $30-billion annually, and knock-off fashions are a significant part of that.
U.S. Customs displays phony merchandise seized in Los Angeles, involving fake North Face and Nike clothing
And there are concerns that Canadian laws are too lax with respect to goods coming across the border.
Jim Holloway, a lawyer with the Canadian Anti-Counterfeiting Network, tells the Financial Post, "Customs officials in Canada have no power to proactively inspect goods to see if they're counterfeit."
"There are only two situations where Customs will act: if the brand owner gets a prior court order; or if the police authorize the action," he said.
Contrast that with Europe and the U.S., where trademarks are registered with border officials, so customs officers can inspect goods with those trademarks to see if they're knock-offs.
"Brand owners train customs officials as to what to look for" says Holloway.
Müller says "the equipment needed to see the pattern is fairly simple, and is already in place at Swedish Customs..."
"It is very difficult for pirate manufacturers to copy the unique combination," Müller told Sweden's The Local - adding there are "loads" of different dye molecules available.
He says the technology could also be used to weave a "virtual bar code" into fabrics, allowing for easier tracking of inventory and better quality control.