The first Firefox OS-powered mobile devices went on sale Tuesday and flew off the shelves as quickly as they came out.

The phones, manufactured by the Spanish company Geeksphone, are not for the average customer. They are intended for developers looking to build and test applications for Firefox OS.

Geeksphone has two models, the Keon at 110 euros ($143) and the Peak at 179 euros ($234). Keon is the budget-oriented model with a 3.5-inch 480x320-pixel screen. The Peak offers a 4.3-inch 960x540-pixel multitouch screen. Both models disappeared shortly after they were put up for sale. A message on the website simply says "is currently out of stock."

The Keon has a 1Ghz Qualcomm Cortex-A5 processor, 3.5-inch multitouch screen, tri-band UMTS/HSPA radio, 3-megapixel camera, GPS receiver, proximity sensor, accelerometer, 512MB of RAM, 4GB of storage, and a 1580 mAh battery, according to CNET, and the Peak has a 1.2GHz dual-core Qualcomm 8225 processor, 512MB of RAM, 4GB of storage, 4.3-inch multitouch qHD IPS screen, 8-megapixel rear-facing camera and 2-megapixel front-facing camera, a 1800mAh battery, and the same GPS receiver, proximity sensor, accelerometer, and tri-band UMTS/HSPA radio.

The objective of releasing the phone to developers was to "test the capabilities of Firefox OS in a real environment with a mobile network and true hardware characteristics like the accelerometer and camera," Stormy Peters, Mozilla's director of developer engagement, wrote on her blog.

Mozilla expects to see Firefox OS devices in the United States in 2014. Firefox OS phones could be slated to be manufactured by other companies such as as ZTE, Alcatel, LG Electronics and Huawei for release next year. Japanese electronic company Sony also says it plans release a Firefox OS phone next year in partnership with carrier Telefonica.