Here are the K12 keycap layout and size overview. The keycap is designed for the Keychron K12 keyboard.
Different rows on the keyboard have different heights and slope profiles and Keychron K12 keycap uses OEM profile with MX style. Therefore the K12 keyboard is compatible with other OEM profile keycaps in the market.
And here is the K12 switch and keycap compatibility table.