Engine Gear tops were introduced with the G-series, and retain the same major design of a typical Beyblade, including a Bit Piece, an Attack Ring, a Weight Disk, and a Blade Base; Engine Gear tops, however, replace the typical Spin Gear with a more advanced Engine Gear, which affects the movement of the top during the battle. Each Engine Gear includes a Turbo Winder to wind-up the engine core. When in action, the Blade Base releases the Engine Gear determined by the Blade Base's clutch lock system. This series of Beyblades were the last ones to be made of plastic parts with the exception of the weight disks. The later ones were semi metal or completely metal. The Engine Gear System and information was released at a BBA World Championship tournament at NASA Houston.