Hello all. I am a new poster here. I am trying to figure out what this fitting is in the attached photo. I need to buy one, but I don't know what to search for until I know what this fitting is called. Is this a standard plumbing fitting, or is it some sort of custom specialty item. It's the white PVC fitting with the 4 bolts attaching it to the tank.

If anyone can assist, I'd sure appreciate it.