NDS 90 6" Black Plastic Atrium Grate, Connects to 6" Spee-D Basin, Pipes, and Fittings: Leaves, mulch, and other debris are trapped at the base of the grate, while the raised dome continues to drain water through from the top. The dome grate has an open surface area of 28.4 sq. in. and flow rate of 87 GPM, and is designed to handle moderate flows of stormwater in mulched landscape beds, natural areas, and window wells. The 6 in. Atrium Grate fits the Spee-D® Catch Basin Drain, 6 in. sewer and drain pipe & fittings, and 6 in. single-wall corrugated pipe for a soil-tight fit. Made of high-density polyethylene (HDPE) treated with UV inhibitors. Hassle-free limited lifetime warranty guarantees the NDS product is free from defects—or we’ll replace it.