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.