RA-N valve housings are used in two-pipe systems (pump hot water systems) to ensure optimal adjustment. They are nickel-plated and come with a red protective cap. RA-UN valve housings are used in pump hot water systems with high differentials, such as district heating or systems with condensing boilers. They are nickel-plated and come with a yellow protective cap. RA-UR valve housings are designed for installation in the return line or in cases of reversed flow. They are nickel-plated and come with a yellow protective cap. No tools are required for the presetting of the valves. A securing ring is available to prevent unauthorized adjustments.