The Pre-filter for Canister Filters comes in a set of 10 pieces along with a keeper for convenient storage. This essential accessory enhances the performance and longevity of canister filters by capturing larger particles before they reach the main filter. The pre-filters are designed to improve the overall efficiency of the filtration system, ensuring a cleaner and more durable canister filter. With the added convenience of a keeper for organization, this set is a practical solution to maintain optimal respiratory protection.