Compatible models: The black purification elements are 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, models W9361122 and W9361123. This washer and wing nut 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 use lead-free and BPA-free materials for the filter housing, ensuring effective contaminant reduction without introducing pollutants into the water. Easy to carry: Ideal for home, travel, outdoor activities, and emergency situations such as water shortages, these filters provide clean, healthy drinking water wherever you need it. Longer useful life: For optimal performance, we recommend replacing the filter pair every 6,000 gallons, depending on water conditions. Note: Measurements are taken manually; please allow 13 cm variation due to differences in lighting and display. Color may vary slightly depending on monitor settings. Please refer to the actual product received.