I'm not 100% sure, about what is different with the motors. I do know that the bigger the number of the motor, ie. 300 and 350, the stonger the motor. With these ferrite motors I would assume that they have more winds inside them and/or bigger magnets. However, some of the sizes of the cans are the same. A gws 300 is the same externally as a gws 400. Again, I'm not 100% but it sounds good......right?