Mastercard is doubling down on its prepaid card business, which it sees as fuel for the rise of many consumer-facing fintech companies.

During its investor day on Thursday, the payments giant said its prepaid card business grew 19% in gross dollar volume from the first half of last year. Furthermore, the company expects its prepaid business to double over the next five years.

According to Michael Miebach, chief product officer at Mastercard, prepaid cards go beyond just reaching underbanked people; they’re also a product that underpins many digital banking startups. “If somebody decides to get into payments and they don’t really know how to do it, we have the card-in-a-box,” he said. “This might sound like it’s some niche business, but it’s not.”

Miebach pointed to Revolut as an example of prepaid cards moving into the mainstream. He noted that the London-based digital-only bank has 6 million customers and is gaining 600,000 customers every month. Mastercard offers a prepaid card through Revolut that features automatic reloads and the ability to transfer funds internationally, and the digital-only bank currently has a waitlist for its upcoming U.S. launch.

In addition to their role among fintech startup product suites, prepaid cards are still an important way to bring in early entrants to the financial system. Miebach spoke about the company’s partnership with Grab, the Singoporean multi-purpose commerce app that covers everything from ride hailing to food delivery. Mastercard announced last year it would provide prepaid cards through Grab, which had a user base of 110 million downloads at the time of the announcement in October. In addition, in July, Mastercard partnered with Uber and BBVA to provide prepaid debit cards to drivers in Mexico. 

Looking to the future, Mastercard mentioned a variety of partnerships it’s using to promote its payments business. In addition to traditional banks, the payments giant has teamed up with companies ranging from fast-food chain Sonic to the fitness watchmaker Garmin to the Brazilian bank NuBank on card products.

Meanwhile, Jessica Turner, executive vice president of product and innovation at Mastercard, said the company is working to ease the online checkout experience for the more than 50% of consumers who still use guest checkout. Through the company’s partner banks’ apps, consumers can link their Mastercard debit or credit cards to online shopping and pay with one click through guest checkout.

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