Water Pressure Regulator. It is designed to protect RV plumbing system against unusually high pressure. It fits all standard water hose & campground risers. It is easy to install and use. Simply connect the regulator to your water hose and then connect the hose to your RV. The regulator will automatically adjust the water pressure to a safe level. This regulator is a must-have for any RVer who wants to protect their plumbing system.