This is a Gear Motor w/Encoder, Support 6V and 12V working voltage, for Projects Such as Robot, Custom Servo, Arduino and 3D Printers.
No-load Speed: 6V - 125RPM / 12V - 251RPM (Plus/Minus 10%)
Locked-Rotor Torque: 6V - 8.9Kg.cm / 12V - 18Kg.cm
Rated Torque : 6V - 2.225Kg.cm / 12V - 4.5Kg.cm
Wiki: http://www.cqrobot.wiki/index.php/Metal_DC_Geared_Motor_w/Encoder_CQGB37Y001