NDS 74 3" Black Plastic Atrium Grate, Connects to 3" Drain Pipes and Fittings as you drain away light flows of stormwater from small mulched landscape beds, natural areas, and window wells. The domed design rises above the surface of the ground to block leaves, mulch, and other debris near the base of the grate while allowing stormwater to flow through the top. The dome grate has an open surface area of 9.4 sq. in. and flow rate of 29 GPM. The 3 in. Atrium Grate fits 3 in. sewer and drain pipe & fittings, 3 in. single-wall corrugated pipe, and 3 in. triple-wall 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.