These are a uniform profile keycap with a cylindrical scoop, much like a Cherry style keycap, but meant for Kailh Low Profile Choc switches. They come to me as clear polycarbonate keycaps and I use a dying process to bring them to life.
These keycaps are 18mm x 18mm so they will NOT fit Choc specific keyboards like the Planck Lite, the Pancake or the Theta. They do look great on boards like the Kyria, Helix, CRKBD/Corne/Helidox, Iris, etc. where the spacing is a normal 19.05mm spacing.