Choke valve is a valve that control fluid flow or pressure by changing the throttle area. The types of choke valve are fixed type, needle type, cage type and orifice type, which adjust the flow and pressure by changing the cross-sectional area of the channel. Usually, the flow rate of the medium between the choke disc and the valve seat is very high, which leads to cavitation on the surface of the choke regulator. In order to minimize cavitation damage, Douson's restrictors are made of materials with excellent cavitation resistance (made of wear-resistant alloy).