Compatible models: The black purification elements are designed to be compatible with Berkey Travel, Big, Royal, Imperial, Crown Series, Propur Traveler, Nomad, King, and Big Series gravity filter systems. Also compatible with Sterasyl and ATC Super Sterasyl filters, system models W9361122 and W9361123. These washers and wing nuts are precision engineered for a secure fit to help prevent leaks. Safe materials: Our replacement filters are made from high-quality natural coconut shell activated carbon. We strictly control the filter material and use lead-free and BPA-free materials for the filter housing, ensuring effective contaminant reduction without introducing pollutants into the water. Portable design: Ideal for home use, travel, outdoor activities, and emergency situations such as water shortages. This filter provides clean, healthy, high-quality drinking water in a variety of settings. Extended lifespan: For optimal performance, we recommend replacing the filter pair every 6,000 gallons, although actual lifespan may vary depending on water conditions. Note: Measurements are taken manually. Please allow a slight variation of 1–3 cm due to differences in lighting and display settings. Color variations may occur; please refer to the actual product received.