The Tecmar Jrcaptain Expansion Sidecard is a vintage computer accessory designed specifically for IBM PC Jr computers. This expansion sidecard, made by Tecmar in the United States, provides additional functionality and compatibility for IBM PCs. While it does not come with any cables or software, it is an essential piece for collectors and enthusiasts looking to enhance their vintage computing experience.

The expansion sidecar dds 128KB of memory expansion (increasing the PCjr total to 256KB), a parallel printer port, and a real-time clock/calendar (which typically requires a battery replacement).