From Sega Retro
The Treamcast is an unauthorised Sega Dreamcast modification which originated from China. It gained notability for being portable, being a smaller size than a regular Dreamcast console and having a fold-down LCD display. Despite being commonly labelled as a "clone", it used original Sega parts and as such is technically more of a modification than a clone in a regular sense.
The Treamcast's firmware allows it to play any Dreamcast game from any region of the globe, as well as CD-Rs and (with special software), MP3 and Video CD formats. However, despite coming from the east, it uses a North American power supply. It is compatible with all controllers, including its own proprietary controllers that come included with the package. These controllers are not compatible with VMUs, however. Widescreen versions of the display also exist.
Though many Treamcasts can be found on auction sides such as eBay, Sega managed to halt the sale of these consoles due to copyright violations.