NDS Dura Slope 663 6" x 2' Black Plastic Channel Drain Grate. The drain grate works with the Dura Slope Channel Drain to capture water flows from hardscapes while blocking leaves and debris in the water from entering the channel and potentially obstructing drain pipes. The drain cover has an open surface area of 25.40 sq. in. per linear ft. and flow rate of 27.00 GPM per linear ft. Made of high-density polyethylene (HDPE) containing UV inhibitors. Rated for NDS Class B loads (up to 175 PSI) when properly installed and ADA compliant. Channel drains, also known as trench drains, are long, narrow drains used for surface drainage of hardscapes. Channel drains collect and convey water to drain pipes, which carry the water downstream to discharge with a pop-up emitter, or to percolate into the ground with a dry well or infiltration trench. NDS channel and trench drains are designed for durability, drainage, and performance, and are a proven alternative to traditional concrete drains.