This design is functionality. It added a small container in the bottle cap and you can put pills inside.Therefore when you drinking water,you will know that you need to take pills.But i think it can put other small items inside the small container.
I like the cheese cloth idea better, this rubber thing looks hard to put back in. If you like this brush, Here's a cheap DIY. put some cheese cloth on the brush and when it's full of hair just pull it off. - But seriously, whoever invented this brush is a