Voila, it's a hollow keycap. I know some people like blank keycaps, so I thought we should take that idea to the next level.
The pink part is the actual keycap which sits on the switch. Imagine there's a stem in the middle of the bottom of the pink.
The gray parts in the image is an optional addon for those of you who like a keyboard with a usable keycap profile and, obviously, costs extra.