NDS 640 6" Black Plastic Square Grate with Low-Profile Adapter Drain for 3" & 4" Pipes. The flared-out design has 14.4 sq. in. of open surface area and 44 GPM flow rate—more open surface area and flow capacity compared to a grate that matches the pipe diameter. Ideal for capturing moderate flows from lawns, landscaped areas, patios, walkways, and under downspouts. The 6 in. Square Drain Grate with Low-Profile Adapter Drain fits 3 in. & 4 in. sewer and drain pipes & fittings, single-wall corrugated pipes, and triple-wall pipes. Grate made of high-density polyethylene (HDPE), low-profile adapter made of high-impact polystyrene (HIPS) treated with UV inhibitors. Hassle-free limited lifetime warranty guarantees the NDS product is free from defects—or we’ll replace it.