What is Choc spacing?
18×17mm vs 19.05mm. Why keycaps can "fit but look gappy."
A classic low-profile gotcha: the caps mount fine, yet the gaps between keys look too wide or too tight. The culprit is key spacing (pitch).
Standard MX pitch is 19.05mm (0.75"). Kailh Choc v1's native pitch is a tighter 18×17mm, and its caps are designed for that. Even when the stem matches, a pitch mismatch throws off the spacing between neighboring caps.
Example: Choc-pitch (18×17) caps on a 19.05mm PCB leave visibly wider gaps. Conversely, MX-pitch caps packed onto a tighter layout can foul each other.
How to choose
Check which pitch your kit's PCB uses first, then match caps to it. Choc v1 is typically 18×17; v2, Gateron low-profile and MX low-profile are typically 19.05mm. Each family page lists its spacing.