Button-group stacked-for-?

Hello,

I’m very new to Foundation so forgive me if I’m asking an obvious question. I’m working on a legacy site and I need to set a custom stack point / break point for the buttons within a group to stack at.

I have the following in my _settings.scss

  1. Breakpoints

$breakpoints: (
small: 0,
smallish: 418px,
medium: 641px,
largish: 1000px,
large: 1200px,
xlarge: $global-width,
xxlarge: 1680px,
);

Should this mean I can add any of these to the “stacked-for-x” class in order to have the desired stack/break point? (underlined in red)
image

so should amending the underlined to “stacked-for-smallish” stack the buttons at 418px?? because when I try this it doesn’t seem to work. . .

Any help would be appreciated,

Thanks