K9 vs. JL 21
They are close but not exactly the same. Most of the demensions are the same, but some of the materials are definitely different. For instance the conrod, the venturi, the heat-sink, the crank-pin, the back plate, and the pinch bolt. Although those are seemingly minor items, and they may all be interchangeable, in micromotor technology the most suttle of changes can make a significant difference.