GOOD FIT: This A10/A11 Pre Filter fits for A10/A11 , A10/A11 Master, for S11 Series Cordless Vacuum Cleaners, helps your vacuum run back to level. DESIGN: 3 pieces A10 filters in one set help you always have one filter ready to use. Just say goodbye to the days when you have to worry about the lack of extra filters. Easy to install: Free your hands from the complicated replacement steps. No additional tools required. Quality above all: Made from state-of-the-art high-strength materials, the A11 filters are designed to outlast. Friendly Reminder: To your vacuum cleaner works properly and optimally, it is recommended to replace the A10 filter every 1-4 months depending on use.