Size 20. All pieces glow in the dark. 1 set = 2 caps, 1 socket, 1 stud. When exposed to light, the glow-in-the-dark snaps will "charge" and retain that light so that they will glow in darkness for a few minutes.
These are not KAM brand. It is unknown how long the glow property will last over time but line drying will help to preserve it longer.
Snaps are packaged by weight so count may not be exact.