It is a double clutch unit with two clutches set on the both side of drum sharing basic design with clutch-brake unit 121-[]-20. Two-stage speed change and forward-reverse operation with hub input, or distribution of motive power with shaft input can be selected. As well as 121-[]-20, it is strongly resistant to a radial load with a wide bearing span that it can be used with high tension by mounting a V pulley or spur gear.