This is the SainSmart 4WD Drive Aluminum Mobile Robot Platform for Robot UNO MEGA2560 R3 Duemilanove,compatible with Arduino.

• Can hold many controllers, drivers, sensors and RF modules etc.
• Supports  plate with controller mounting holes, 2 dof pan.
•  Tilt holds down groove, collision switch mounting hole, can be added with sensors.
• Elastic rubber tires. Damping, gripping, and wear-resisting.
• Light weight, high strength and no deformation characteristics. 
• Unique design and color.