Insert for a size 28D pill bottle. Used to separate and store two different prescriptions in the same bottle. Also great for prescriptions requiring intermediate doses (one and a half tablets). Recommend poking a small hole in the bottom of the pill bottle for air release as you press the insert in, as it's a pretty tight fit. 

The insert is recessed a few millimeters from the bottle's top edge, as the model is meant to be used with the original bottle lid using the male threads (top side of the lid, see picture).