Filler ring for lego storage boxes

So, Lego makes these cool storage boxes, like this:

https://shop.lego.com/en-US/LEGO-4-stud-Blue-Storage-Brick-5001383

The problem is that they have a recess in the bottom that little pieces fall down into. This ring fills that gap, so the pieces don't fall in. The recess in the Lego part is slightly tapered, so just press this in and it will hold well. It should sit ever so slightly recessed.