Made of highest quality structural foam polyethylene with UV inhibitor. For use in all areas of vegetation and trees. Use in non-traffic areas where lawn mowers are excluded. 6 in fits 6 in S/D pipe fittings, 6 in bell end, 6 in corrugated and 6 in catch basins. Open surface area of 23.91 sq-in. Grate opening of 5/16 in, SDR 35, 2729 S&D triple wall.