Carbon Replacement Pre-filter for Honeywell Model HPA300 (3 Activated Carbon Pre-Filter pack) Perfectly fitted for Honeywell Model HPA300. (Not come up with Universal Size). The pre-filter has a dimension (mm) Length 439 X Width 360 X Thickness 5. No need to make any further cutting, it saves your effort and avoid messy jobs. Help to capture certain airborne germs, remove unpleasant odors and allergies. It has the ability to filter off a room size of around 465 sq.ft. Made up of nature material, high density coconut shell activated carbon.