If you need a solid base for your Actobotics project, the round base is perfect. It's nearly 4" in diameter and 1/8" thick aluminum. It utilizes both the 1.5" and 0.77" hole patterns for connecting hubs, and other Actobotics parts.
Actobotics is a robotics building system based around extruded aluminum channels, gears, precision shafts, and ball bearings. Thanks to the two standardized hole patterns, nearly all Actobotics components can be intuitively connected together. The wide range of components makes building complex electromechanical prototypes or finished projects a reality.