1 Allows micro engines that are 3.8cm or 5.7cm long to be used in a stock (8.9cm long) micro engine mount. 2 Engine mount adapters include engine tube, centering rings, thrust ring, and engine clip. (EA-1118 also includes set of 10.5mm engine spacers.) IMPORTANT: Just because an engine will fit in a rocket does not mean it is safe to launch the rocket with that engine. Always ensure your rocket is below the maximum mass allowed for the engine you are using.