Air Box Refill 4Maintain optimal performance of your filter using refill cartridges. They serve as a replacement for cartridges used in Air Box filtration systems. The package consists of 4 high quality cartridges made with 100% activated coconut charcoal. Each cartridge is airtight to ensure hassle free operation. They are perfect to use in residential, industrial, and commercial operations. Features: Easy to install, use and maintain 100% premium activated coconut