Apple’s promised USB-based OS X 10.7, or Lion, installer made its way to the company’s online store on Tuesday. The USB flash drive includes the full Lion installer and, unlike the standard Mac App Store installer, doesn’t require an Internet connection.

Lion was released on July 20 and was touted as the first Mac OS ever to ship without physical media. On launch day, however, Apple announced that it would, in fact, sell a physical installer.

Instead of offering a DVD version of Lion, Apple chose to sell the OS on a USB flash drive. The decision to drop optical media-based installers made sense because the company is moving away from DVD drives in its computers — first with the MacBook Air, and now the Mac mini.

While installing Lion from a USB stick may have the convenience of not requiring an Internet connection, it also comes with a limitation in that reinstalling at a later date must be done from the USB drive.

Apple’s product description states, “When you install OS X Lion using the USB thumb drive, you will not be able to reinstall OS X Lion from Lion Recovery. You will need to use the USB thumb drive to reinstall OS X Lion.”

The OS X Lion USB Thumb Drive is priced at US$69 and is available through Apple’s online store.