Google is letting Glass Explorers swap in their first-generation wearable device for a newer model if they want to try out a faster, more durable device that also works with prescription glasses and comes with new accessories. While Explorers won’t have to pay anything on top of what they already paid for Google Glass to make the switch, only those Explorers who bought their units before October 28th can apply. The hardware upgrade is not mandatory though, Engadget reports, although in its notification Google warns Explorers that future features and accessories may not work with first-generation Glass units. In addition to Google inviting Explorers to make the switch, a Google employee posted images on Google+ showing a Glass unit mounted on prescription