docs/_scss/_breakpoint.scss

$sm-min-width: 576px;
$md-min-width: 768px;
$lg-min-width: 992px;
$xl-min-width: 1200px;

@mixin sm-width {
  @media (min-width: $sm-min-width) {
    @content;
  }
}
@mixin md-width {
  @media (min-width: $md-min-width) {
    @content;
  }
}
@mixin lg-width {
  @media (min-width: $lg-min-width) {
    @content;
  }
}
@mixin xl-width {
  @media (min-width: $xl-min-width) {
    @content;
  }
}