A: The form of the structure can be divided into plug adapter plug valves, self-sealing plug, plug, plug valves and oiling four. By channel form can be divided into straight-plug, three-way and four-way stopcock plug three. Among them, straight-plug is mainly used to cut off media; three-way stopcock is mainly used to adapt media orientation or assign different medium; four-way plug valves are mainly used to change the media flow or distribution media.