: Measured by the number of beam holes they span (e.g., 3-length or 5-length axles), these are used to connect wheels and gears.
For the physical body of the robot, the authors emphasize moving beyond basic bricks to specific Technic elements for stability: Building Robots With Lego Mindstorms: The Ultim...
: The predecessor to the EV3, which introduced more advanced sensor and motor connections. : Measured by the number of beam holes they span (e
In "Building Robots with LEGO Mindstorms: The Ultimate Guide" by Mario and Giulio Ferrari, a "proper piece" for starting your build often refers to the core structural components or the "brains" of the robot. 3-length or 5-length axles)