Small in size and light in weight ,easy instillation and maintenance .it can be mounted wherever needed. siple and compact construction ,quick 90 degrees on-off operation. minimized operating torque, energy saving. Flow curve tending to straight line, excellent regulation performance. long service life, standing the test of tens of thousands opening/closing operations. Bubbles-tight sealing with no leakage under the pressure test, wide selection of materials, applicable for various medium