Apple is awarding an additional $250 million to Corning, the manufacturer that supplies the glass to Apple (and many others) to use in its iPhones, iPads, and Apple Watches. The money comes from Apple’s Advanced Manufacturing Fund, which already provided $200 million to Corning back in 2017. Apple has now committed to spending $5 billion as part of the fund, which aims to fuel “a new era of technology-driven manufacturing in the US.”

Neither Apple nor Corning says exactly what developments the new investment will be put toward, only hinting at future devices. “The combined investment supports Corning’s research and development into state-of-the-art glass processes, equipment and materials integral to the delivery of next-generation consumer devices,” reads the press release issued by Apple.

Glass manufacturers are working to produce bendable glass for folding devices

The investment takes place as glass manufacturers attempt to produce bendable glass for future folding devices to replace the plastic screens used in the first generation of foldables. Bloomberg reported earlier this month that Samsung is testing an ultra-thin bendable glass for its successor to the Galaxy Fold, and Corning has spoken previously about its own efforts to produce glass that’s thin enough to bend without becoming too fragile. Early rumors have suggested that Apple is working on a foldable for release as early as 2020.

Officially, however, Corning is keeping coy about what it intends to put the new investment toward. The company’s chairman Wendell P. Weeks said that the fund award will allow the company to “develop groundbreaking new glass innovations” and create “vital new capabilities for end users.” Maybe that just means that we’ll get even tougher glass for future devices. Apple says that its latest iPhone features the “toughest glass ever in a smartphone,” and it produced an ad where its latest phone withstood the impact of all manner of household items as proof.