Its a JTK tray. Smaller variant that better fits keycap profiles so they won't flip over.
Closes and opens and holds your keycaps nice and snug so you can keep your extra keycap sets nice and organized. Ideal for 'standard' profiles (GMK, OEM's, ePBT, JTK).
Each tray holds your average 60-75% kit. I recommend getting 2 at a time to cover an entire average GMK set.
Note: This will still fit your low profile keycaps but they may flip over if shaken.