I don't work at the facility that makes them, but I'd have to disagree. Besides having the same specs, if they were truly the "same servo" just with a different spline, the 6040 would be much louder and almost always require a cap or external bec like the 1258. I rarely hear of a 6040 causing any glitching or brown out issues. The 3 6040 servos that I run are very quiet and have never given me a single issue, and that's running with a Spektrum radio and used to run a MMP esc (with no issues). Not saying I feel the 1258 is crap. I'm just not convinced that they're the same servo.