The Dreamcast Virtual Memory Unit VMU is an external attachment for the Sega Dreamcast console, manufactured by SEGA. It is designed for NTSC-J format memory cards and provides wireless connectivity with a range of less than 5 meters. The VMU is a lightweight unit weighing 30g and comes with a lifetime manufacturer warranty. It is compatible with Sega Dreamcast consoles and memory cards, offering an additional layer of storage capacity for games and media.