4", Sand, Round Structural Foam Polyolefin Grate With UV Inhibitors, Open Surface Is 3.85 SQ IN And Has A Flow Rate Of 5.04 GPM, Fits 4" Sewer & Drain Pipe & Fittings, 4" Corrugated Pipe, & 4" Triple Wall Pipe, Recommended For Pedestrians, Bicycles, & Wheel Chair Traffic.