[Gritt]

Lightweight => 10 KB

I'm actually more looking for a grid system using flex in a few bytes

[Zealotux]

It's written is Sass, you can simply import only the components that you need such as the grid.

[cageface]

CSS grid works in all modern browsers now. It’s totally change the way I do layouts and is way less cumbersome to just use directly than these other hand rolled float or flex grid systems.