The 21986 accessory pack from irobot is a 3 pack which contains 3 side brushes and 6 hepa filters giving the option to keep the inside of your 700 series irobot vacuum the side brushes can get damaged easy by picking up hard objects and odd shape objects leaving the brushes harder to pick anything up the filters inside the vacuum over time will get blocked up and will lose performance so the filters need changing from time to time with the accessory pack you can both filters and side brush a