The first number is the rotor diameter. 12.5 is higher torque than 12.1
Yes, correct more big size more torque
The second number 7.25 vs 5 is?
This number shaft diameter. 7.25mm is ROAR spec rotor rule. 5.00mm use to Modified motor. thin shaft more magnet mass. more torque
Third number 24.2 is shaft length
Yes correct more long size pick throttle more smooth with more bottom range torque.
Then there are spec rotor with lettering S, W, Y and Z
This numner magnetic strength Y=38UH, Z=42UH , Other rotor all 35UH S,W is no magnetic strength number. high number more high magnetic strength
Add if same size with same magnet rotor titanium rotor vs Stainless rotor titanium shaft more high RPM with fast pick up, But magnetic strength going down. Stainless shaft more torque than titanium shaft rotor. But is a heavy weighty pick up slower than titanium shaft
* Sting and Specter series use to Modified rotor Max 12.8mm DIAMETER