An animal cage box has a grommet for passing a watering conduit through a box side wall. The grommet is removably attachable at an opening through the side wall, using a non-round configuration by which the grommet is aligned for insertion into a non-round opening, and turned to hold the grommet in place. A flange on the grommet body rests against one face of the side wall. The non-round configuration includes one or more tabs that can be cut from the flange and are displaced axially by a distance equal to the side wall thickness. A hinge flap that can be grasped in the fingers helps to hold, align, insert or remove and twist the grommet relative to the side wall. The disclosed arrangement further minimized the cost of using inexpensive disposable cage boxes because relatively expensive grommets, for example of stainless steel, can be cleaned and reused.