The open-closed piece of the valve is a round-disk butterfly board and, by rotating around the axis of its own inside of the valve body, carries out the open-close or adjusting function. It features: 1)Simple structure, small volume and light weight; 2)Quick open-close, labour saving and small fluid resistance; 3)Good adjustable performance, can be adjusted flexibly within 0-90° , suitable for the pipeline of water supply and drainage, high building, firefighting, petroleum, chemical industry, medicine, food etc. Trades to act as open-close or adjustment.