extremely tough to get into existing walls. You need to somehow glue the 90 to the inlet while it is in the wall. No way to only glue male end on this puppy as electical box is very close to pipe fitting. Managed to do it but one you have glue on fitting you only have one shot at getting it right. Attaching pipe to 90 also requires 2 people. One in attic to push down and one at bottom to guide, glue and twist.