DC 12V Reversible High Reduction Electric Motor 15-200RPM Outer Diameter 20MM(200RPM)

I ran it a a range of Voltages from 2.3v to 12v. No problems (yet).I plan to use it at 2.5v to 5v direct power though, I may do PWM from an Arduino. If I don't do PWM, I'll use a Switching Relay controlled from Arduino. I could Not hold the Shaft from turning at 2.3v...

half decent motors, good for the price but no useful for much in real life

I ordered a 30rpm, and a 100rpm motor. I hooked the 30rpm motor up to my variable DC power supply, set to 12V, and it worked great in either direction. It had quite a bit of torque too, and will be perfect for future projects. I did the same with the 100rpm, and it seems to be DOA. Started a return, and I am getting a replacement sent to me. Otherwise they seem like great compact motors. The 30rpm motor also ran very well at 9V which is great, because I plan on using a 9v battery to power it.Replacement was sent in 2 days, and it works fine, but it still sucks I had to go out of my way for a the return, but it happens.

I used this motor on two models; a Ferris wheel and a midway swing. They both worked very well probably more power than needed.

This motor functions just fine, but worth noting it is somewhat loud. Easily heard from 10 feet away.

However I need the screw size to mount it to something..

Fits and works in a golden key machine

The shaft size is 4mm with a flat side. I am powering mine with 9 volts. It's a bit noisy but works great.