Get the best suction power out of your Kogan C11 & Z11 Pro Cordless 29.6V Stick Vacuum by replacing the filter every few months. Don’t let a clogged filter restrict your Kogan C11 & Z11 Pro Cordless 29.6V Stick Vacuum suction power! By replacing your filter every few months, you can help ensure your C11 vacuum is trapping 99.97% of fine dirt, allergens and pollen to help protect your family from respiratory stress triggers.