50% resets, 50% micro-framework, 100% awesome.
Very rough estimate
FOX CSS only includes the essentials: it won't dictate how your site must look, but it will rather provide some tools to ease your life. The result weighs 23kb minified.
Each class in this framework is namespaced. This means that you can use it in association with any other framework you want without worrying about breaking anything.
FOX CSS is built with modularity in mind. This means that each part of it is not necessary for the rest to work. Don't like grids? Just remove the corresponding Sass partial!
A grid system based on Flexbox, which offers a lot of layout possibilities (make sure to check the docs for examples). Side bonus: it also comes with IE9+ support :)