PVCCROSS34 Schedule 40 PVC Cross, 3/4 Inch. A cross is a plumbing fitting that allows you to connect four sections of PVC tubing and pipe. Each of the four connections has slip fit connections measuring at 3/4 inch, meaning that the PVC tubing will slip easily into the cross fitting. This fitting is specifically for use with 3/4 inch schedule 40 PVC pipe. These fittings are great for water transportation applications such as irrigation and sprinkler systems. However they should never be used for gas or compressed air applications.