The Holmes 9000233 is the correct replacement prefilter for the following air cleaner models:
The Holmes Foam Air Cleaner Prefilter 2pk 9000233 is a replacement foam pre-filter for the Holmes Model HAP422 Air cleaner. This Holmes air filter measures approximately 4" x 19 1/4" x 3/8" and removes larger particulates from your indoor air. This 2 pack of carbon pre-filters should be replaced every 3 months for the best air filtration results.
Holmes Foam Air Cleaner Prefilter 2pk 9000233 specifications: