Plastic moves a lot easier than metal... by that I mean that with the plastic horns or plastic spindle there is some minor flexing of the plastic which helps the horns go on smoother than the metal ones. With the metal on metal I'd say it needs to be lined up perfectly and both the horn and spindle free from any debris.

Before putting too much force (some force should be OK without causing any damage) I would compare the metal horn to the plastic one and see if they look pretty much the same. It may also pay to add a little lube to the spindle and horn to aid in them fitting together nicely (it's amazing how much a little lube can help when trying to push something in to something that's tight).

Yeh, I noticed that they worked on the HiTec not Futuba. You BOTH gave me Great advice. The FACTORY told me that they don't sell 24T, ONLY 25T. So, that was there horn that was supposed to fit. But, it did not go on unless i forced it. And I had to PRY it off.

Thank You Both!

Anybody else have any comments?

i notice some plastic horns can be squished on even when they arent the right tooth count. the metal horns wont do it though. Only spend your money on a metal horn on something you see there will be heavy stress on the servo. you will want to consider using pushrod ball joints to allow for a small amount of play but still be stiff and strong.

Thanks, Josh! I have heard plastic horns for plastic servos and metal only horns for metal servos.

I put baby oil on the horn and managed to get it on. But, it was very snug. And I had to pry it off with a screwdriver.

@Anthony, on the coupler, I bought a 4mm which would be 3/16", no teeth.

@moviemaker , no you can mismatch metal splines with plastic horned or the other way around. The metal parts are machined for accuracy and strength. The plasticb ones are injected molded in a may that they must be pushed on with a little force for a snug fit because nylon and abs plastic horns stretch a little when you install them.

Thanks for the info.