Just a little note, if older Airtronics servos are found, they are still usable by changing the plugs. By looking at the older black plug you will notice one of the three has a red stripe. That would be the positive wire, the next adjacent wire is the negative and the last wire is the signal. I have bought several older sailplanes that came with older Airtronics servos and have changed plugs to match my Hitec Optima receivers without any issues. The older Airtronics 94141 metal gear servos were everywhere in the '90s, still a great servo in my opinion.