Homelite UT33600 Trimmer (5 pack) Replacement Foam Air Filter # 900952011-5pk Genuine OEM Replacement Filters (5 Pack) Compatible with Ryobi and Homelite Brand String Trimmers and Brushcutters Its purpose is to filter out dust and debris from contaminating the carburetor and engine. Brand New in Bulk Packaging Please refer to list below for Compatibility.