4 Inch PVC Sewer & Drain Tee Cross Fitting for SDR-35 S&D Pipe, HUB Connections. A cross is a plumbing fitting that allows you to connect four sections of SDR-35 PVC pipe. Each of the four connections has slip fit connections measuring at 4 inch, meaning that the PVC tubing will slip easily into the cross fitting. The fitting is specifically used in order to connect four sections of SRD-35 PVC pipe or fittings. These fittings are great for sewer and drain applications such stack vent (aka. stink stack, soil stack or stink pipe) and other drain applications within a residence or commercial property. However they should NEVER be used for gas or compressed air applications.