Compatible With: Royal 001331007 410044001 902185003 562161003 ER20000 Pro-Series Corded Cyclonic Stick Vac Vacuum Cleaner. There are three filters in each pack. These filters are washable. Clean the filter by hand washing with water until it is clean. For best results, clean after each use. Each time the dirt cup is emptied, the filter should be cleaned (Filter will be discolored after use. This will not affect the filter's performance.) It's very important that you let this filter completely air dry before reinstalling it into the vacuum cleaner. Do not operate cleaner without filter and do not operate cleaner with a wet or damp filter. Failure to do so can cause the motor to fail if any moisture enters it. WARNING: Always dry filter for 24 hours before replacing. Do not use detergent or hot water to clean filter.