The R-3710 Series Restrictors are available with fixed and variable sized orifices and various styles for convenience of installation. The fixed restrictors come in two sizes and are color coded for easy identification. A restrictor with a .005 in. (.13 mm) orifice is red and a restrictor with a .007 in. (.18 mm) orifice is aqua. The size and type of restrictor to be installed in a system must be selected with discretion in order to insure proper balance and operation of the devices within the system.