Original Hoover Secondary Filter, Spectrum, PowerMAX, WindTunnel & Futura Canister #38765009. Hoover Futura and Spectrum secondary filter 1 pack contains a single layer white filter 38765009. Measures 5 3/8"" x 4"" inches. Fits fits behind the paper bag in canister vacuums including these popular models: C2089---, S3601050, S3630---, S3630050, S3639---, S3639050, S3646---, S3649---