SI Pipes Ultra Carbon Filters are made in the U.S.A. by professional glass artists using high-quality glass and ground joints. Filters can be filled with Organic Cotton or Virgin Coconut Carbon. Help your body experience the benefits of a cooler, cleaner delivery method and still retain the potency and flavor of your medicine. Scientific InhalationsUltra Carbon Filter Adapter is handmade with high-quality (Schott or Simex) glass in California. The inner dome filter has four slits on the side with a cross-slit on the top. These slits are designed to allow the exact amount of (air/flow) to pass through.