NDS 920B 6" Satin Brass Square Grate with Low-Profile Adapter Drain has an open surface area of 11.6 sq. in. and flow rate of 35 GPM; drains light flows from small lawns, landscaped areas, patios, and walkways. The 6 in. Square Drain Grate with Low-Profile Adapter Drain fits right onto 3 in. & 4 in. sewer and drain pipes & fittings, single-wall corrugated pipe, and triple-wall pipe. The rust- and corrosion-resistant brass grate is fitted onto a high-impact polystyrene (HIPS) low-profile adapter treated with UV inhibitors. Hassle-free limited lifetime warranty guarantees the NDS product is free from defects—or we’ll replace it.