And in _vars.scss:

```scss
    (mobile  gs-span(4) + $gs-gutter/2*2)  // 340px
    (tablet  gs-span(8) + $gs-gutter*2)  // 660px
    (desktop gs-span(12) + $gs-gutter*2) // 980px
    (wide    gs-span(16) + $gs-gutter*2) // 1300px
```