No one wants to pay full price for anything—especially for printer ink cartridges. That’s why many consumers turn to third-party printer ink cartridges, or aftermarket inks.

In Consumer Reports' most recent annual printer survey, 37 percent of respondents said they have tried third-party printer Copier Toner Kit, which can cost much less than name-brand products. It’s easy to see the appeal of third-party ink: Ink for some printers can end up costing almost $700 over five years, according to CR's calculations.Third-party printer ink was in the news this spring when the Supreme Court ruled in Impression Products, Inc. v. Lexmark International, Inc. that third-party companies could refill toner cartridges originally sold by a printer manufacturer.

Lexmark had argued that Impression was violating Lexmark patents by refilling and reselling such cartridges. Neither company would comment on the lawsuit. And Lexmark, HP, Epson, and Impression Products did not agree to discuss ink prices with Consumer Reports.

“We believe this is a positive step for competition, innovation, and consumer choice,” says Jessica Rich, Consumer Reports’ vice president for consumer policy and mobilization. “It’s a win for consumers and small businesses.”

However, although many consumers like third-party printer inks, the products don’t always work well, according to Consumer Reports’ testers. Here’s what you should know before buying third-party ink cartridges:n CR's printers survey, 63 percent of respondents who used aftermarket cartridges say they’re just as good as name-brand cartridges, while 36 percent think they’re not up to par.

Rich Sulin, who leads CR’s printer-testing program, says that some samples worked without any problems but that other samples of the same products “set off warning messages from their printer or failed to print a test page.” Additionally, he says, “some aftermarket inks worked initially but quickly clogged printer heads.”

Sulin says to make sure the vendor provides a money-back guarantee, and he advises you to use the ink or toner as soon as possible after a purchase.

Consumer Reports doesn't rate third-party inks because the marketplace is so fractured—a large number of manufacturers offer a rapidly changing lineup of products for different printer models, making comparisons difficult.