ARS 1050 RB is the most common filter and filter element normally found before the refrigerant dryer in most applications. It is commonly refered to as the 'general purpose' filter element. The ARS 1050 RA is an very fine filter for oil removal, and air from this filter is generally classed as oil free. The ARS 1050 CA is an active charcoal filter for odour removal and when used with the other two filters will give air as clean as it gets. Only those living on a Scottish island will breathe cleaner air! There is a wall mounting kit (XAS 4). A Pressure Differential Gauge is available to monitor the state of the filter (XAM 100). Generally the elements will benefit from being changed every 12 months.