Google Glass is a type of wearable technology with an optical head-mounted display. It was developed by Google with the mission of producing a mass-market ubiquitous computer. Google Glass displays information in a smartphone-like hands-free format. Wearers communicate with the Internet via natural language voice commands. Google started selling Google Glass to qualified "Glass Explorers" in the US on April 15, 2013, for a limited period for $1,500, before it became available to the public on May 15, 2014, for the same price. Google provides four prescription frame choices for $225.00 U.S and free with the purchase of any new Glass unit. It is necessary to remove a small screw in order to move the Google Glass from one frame to another. Google entered in a partnership with the Italian eyewear company Luxottica, owners of the Ray-Ban, Oakley, and other brands, to offer additional frame designs.