1. 4PCS Water Filter Replacement for BERKEY Black Activated Carbon BB9-2 Filters for Gravity-Fed Water Filter System P20250110581 2. [Filtration precision up to 1 Micrometre]: In order to good filtration performance, this filter elements uses coconut shell activated carbon as the filter material, with a filtration precision up to 1 Micrometre. Efficiently removes impurities such as sand, rust, sediment, odor, etc., while effectively absorbing residual chlorine, with a removal rate of more than 99%. 3. [Compatible Models]: The filter can replace the for water filter. Compatible with for gravity filtration systems including Travel, Grand, Royal, Imperial, and Crown Series. The precision design of the washers and wing nuts ensures a secure connection and prevents leakage. No primer required, it can be installed and used after replacement, saving early flushing work. No low traffic issues. 4. [Durable Lifespan]: To extend the life of your device and get good performance, we recommend you replace the filter every 6,000 gallons (depending on the quality of the tap water ). Please note that you must fully submerge the carbon filter once a week in order for the drip system to siphon properly. 5. [Note]: Before installing the filter, soak and clean the filter to remove residual manufacturing dust. 6. Colour: Black 7. Material: coconut shell activated carbon 8. Package Contents: 4 water purification filter elements 9. Only the above package content, other products are not included. 10. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.