NDS Dura Slope DS-221 6" x 2' Galvanized Steel Channel Drain Grate. Made of tough, weather-resistant galvanized steel, the drain grate prevents leaves and other debris from entering and potentially clogging drain pipes. Works with the Dura Slope Channel Drain to capture runoff from hardscapes. The grate, also known as a drain cover, has an open surface of 23.09 sq. in. per linear ft. and flow rate of 70.64 GPM per linear ft. Rated for NDS Class C loads (up to 325 PSI) when properly installed. 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.