Abstract: A cartridge includes a housing having two orifices for rotatably receiving two stems respectively. The stems each has a gear extended inward of the housing. A gear transmission device is coupled between the gears of the stems for allowing one of the stems to be driven by the other stem with a greater speed, and for allowing the other stem to be driven by the one stem with a greater torque. The gear transmission device includes three gear members rotatably secured in the housing and each having two gear portions of different sizes for engaging with the gears of the stems.