This kit contains all available orifices (No. 4 - .040 In., No. 5 - .070 In., No. 6 - .0935 In., No. C - .1285 In., and No. D - .1850 In.) along with the angle steam valve. This allows you to size the valve for installation in any room, maximizing venting capacity. For use on radiators near boiler and in warm rooms. For radiators in room in which the thermostat is located. Use on radiators farther from boiler and in cold rooms. Use when large amount of air must be vented such as on radiators with particularly long branches and on very large radiators. Self-adjusting thermostatic control, float to prevent water escape, reduces radiator noise, cuts fuel consumption, assures even heat distribution, lowers operating costs.