By far, the Cox TD010 is the smallest production engine ever made. Cox didn't stay in business for as long as they did my making a lousy product. The Cox line of engines are some of the highest quality engines ever made. The machining tolerances were 25 millionths of an inch. The first company where you didn't have to buy the piston and cylinder as a set. They were interchangable. The Cox TD 049 and 051 were THE engine to use in class 1/2A and A free flight for 40 years. The TD 049 held the 1/2A speed record for at leat 30 years. The Babe Bee 049 was made in the miilions, more than any other engine. The break in was ONE MINUTE. I used dozens of them. They were easy to use and well made. Owned Cox engines from the little 010 up to the Special15 MkII as well as the conquest 15. NEVER had a bad one. I still have a 4 gallon fuel box full of them New and Used.