Powermasters feature a humanoid figure that transforms into an engine. The engine is then placed into a special slot that enables the transformation into the robot mode. Also see the Japanese entry for Super Ginrai, which carries the idea one step further. See 1987 entry for Headmasters details. The engine is then placed into a special slot that enables the transformation into the robot mode.
Pretenders have an outer shell which opens to reveal the transformable robot inside.
The outer shells are listed in parenthesis. European Autobots Grand Slam, Raindance, and the Autobot Micromasters were not available in Europe at this time. Groundbreaker, Sky High and Splashdown were not released in the United Kingdom. Godmasters feature a humanoid figure that transforms into an engine. The engine is then placed into a special slot that enables the transformation into the robot mode.