4mm coreless motors are usually 408 and 412, while 410 and 414 are pretty rare. The shaft diameter is mainly 0.7mm, but there are also 0.6mm ones. Right now, motors with 0.6mm shafts are mostly seen on Horizon-Hobby linear servos. I've redefined the motor codes a bit: the first digit is the body diameter, the middle two digits are the body length, and the last digit is the shaft of motor. My 4mm motor gearbox usually come with the most powerful 4127Y or 4087Y motors.

The specifications of several types of 4mm coreless motors. Some parameters provided by manufacturers, some parameters tested by myself, do not represent accuracy, and are for reference only.

4127Y

4127L

4127S

4126S

4126L

4087Y

4087L

4087S