STI™ Gasketed Sewer Fittings from Plastic Trends are now fortified against stress and breakage to a degree never before available in a PVC sewer fitting. The branch intersections of the tees, wyes and sanitary tees in Plastic Trends' SDR 35 line of STI Gasketed Sewer Fittings have been strengthened. The wall thickness of the 4" branch is now 192% thicker than SDR 35 and 115% thicker than SDR 26. The wall thickness of the 6" branch is now 94% thicker than SDR 35 and 46% thicker than SDR 26. The gasket is set deep in the hub for greater protection from angular deflection, and socket depths are designed for increased pipe support. Plastic Trends.