These filters are for the Riccar 1700, and 1800, and Simplicity S36, S36L, S38, and S38L full size canister models. The filter set included the pre-motor charcoal filter that is located behind the bag, as well as the exhaust HEPA filter that sits on top of the machine. These filters should be replaced at least once a year, or whenever the filter change indicator alerts you, located on the handle of the hose. These are Envirocare Replacement Riccar/Simplicity filters. Riccar and Simplicity are sister companies, and their vacuum cleaners come off of the same assembly line, they take the same filters, belts, and bags 99% of the time. 1 HEPA Filter, and 1 Charcoal Filter included with each set.