The 30:1 Micro Metal Gearmotor comes with 30:1 gearbox attached. Speed at rated voltage 6V is 440rpm, that is pretty fast! The gearbox output shaft is a D-shaped with 9mm long and 3mm in diameter. There are several types of wheel that you may use together with this motor.
All SPG10 motors are DC brushed motor with gearbox. The rated voltage is 6V, higher voltage will provide higher torque and higher speed, but it will shorten the life of the motor.