Allergen filtration cartridge filter fits in dirt cup of all HooverFoldaway models in the 51000 series and Turbo Power 3100 includingthese popular models: U5162906, U5162911, U5164900, U5165900, U5167900,U5167950, U5170900, U5172900, U5173900, U5173950, U5174900, U5175900,U5175950, U5176950, U5177900, U5178900, U5179900, U5179906, UH40155,UH40185, UH40190. Approximately 5 1/2" wide x 2 3/4" inches tall.