The Pololu Zumo chassis is a small, tracked robot platform that is less than 10 cm on each side, allowing it to qualify for Mini Sumo competitions. The chassis is composed of black ABS and features a compartment for four AA batteries and sockets for two micro metal gearmotors. It ships as a kit with two silicone tracks, two drive and two idler sprockets, a 1/16″ acrylic mounting plate, and mounting hardware. (Motors and batteries are not included.)
The Zumo chassis kit contains the components necessary to build a small, high-performance tracked robot platform that is compact enough to qualify for Mini Sumo competitions. The chassis is made from black ABS plastic and has sockets for two micro metal gearmotors and a compartment for four AA batteries (motors and batteries are not included). The battery compartment terminals protrude through the chassis and can be accessed from the top side. A black acrylic plate is included with the chassis. This plate holds the motors in place and can be used for mounting your electronics, such as your microcontroller, motor drivers, and sensors.
More technical information at Pololu.