Special black weighted PVC compound ensures durability, reliability and sink-ability while in use and is ideal for trouble free delivery of air to pond aeration systems. Remains flexible for use in a wide range of temperatures. Greatly reduces installation time, requires no maintenance following instructions. Naturally sinks without the use of additional weights or anchors. Great for use in pond and lake aeration, water recirculation, ice clearing, wastewater lagoons and commercial hatcheries.