Compatible with: Hoover Anniversary Self-Propelled U6485900, U6485900B, UH50000, UH50005B Bagged Upright Vacuums, Windtunnel Secondary Filter part # 38765019 / 38765-019, 38765023 / 38765-023 Replacement. The package contains four filters. The secondary filter is located behind the grill in the bottom of bag compartment, protects the motor from dirt particles. If filter becomes dirty, pull off grill and lift out filter. Hand wash filter in cold water with mild detergent, then air dry. Do not operate the vacuum with wet filters. Should be cleaned with each bag change and replaced every 3 to 6 months.