CNBTR 30 Teeth Motor Metal Gear Wheel6mm Hole Diameter Modulus 1 Steel Gear Pack of 2 A great replacement for your damaged Gear. Made of Metal. Inner hole diameter: approx. 6mm / 0.24" Total Height: approx. 18mm / 0.71" Used widely in milling machine, CNC engine lathe, gear shaper, hobbing machine, drilling machine or other machinery transmission occassions.