maybe someone will find this info useful. if any of this info is off, please post up and i will edit it, or if your a mod or admin, just edit this post lol.

Servo output shafts

23 tooth spline - Sanwa / Airtronics / KO / JR
24 tooth spline - Hitec
25 tooth spline - Futaba / TT / ACE / HPI

Spline (teeth (gear Mesh) on Servo's output shaft)
23 teeth on the spline
-KO Propo
-JR Propo
24 teeth on the spline
-Tower (System 2000)
25 teeth on the spline
-Tower (System 3000)