<ul class="nav nav-tabs">
  <li class="nav-item">
    <a class="nav-link active" href="#">Active</a>
  </li>
  <li class="nav-item">
    <a class="nav-link" href="#">Link</a>
  </li>
  <li class="nav-item">
    <a class="nav-link" href="#">Link</a>
  </li>
</ul>You don't need to remember all CSS classes. Just use the Bootstrap Editor instead.
/* _nav.scss:32 */
.nav-tabs {
  border-bottom: $nav-tabs-border-width solid $nav-tabs-border-color;
  .nav-item {
    margin-bottom: -$nav-tabs-border-width;
  }
  .nav-link {
    border: $nav-tabs-border-width solid transparent;
    @include border-top-radius($nav-tabs-border-radius);
    @include hover-focus {
      border-color: $nav-tabs-link-hover-border-color;
    }
    &.disabled {
      color: $nav-link-disabled-color;
      background-color: transparent;
      border-color: transparent;
    }
  }
  .nav-link.active,
  .nav-item.show .nav-link {
    color: $nav-tabs-link-active-color;
    background-color: $nav-tabs-link-active-bg;
    border-color: $nav-tabs-link-active-border-color;
  }
  .dropdown-menu {
    // Make dropdown border overlap tab border
    margin-top: -$nav-tabs-border-width;
    // Remove the top rounded corners here since there is a hard edge above the menu
    @include border-top-radius(0);
  }
}Code copied to the clipboard.
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/* _nav.scss:32 */
$nav-tabs-border-width
$nav-tabs-border-color
$nav-tabs-border-width
$nav-tabs-border-width
$nav-tabs-border-radius
$nav-tabs-link-hover-border-color
$nav-link-disabled-color
$nav-tabs-link-active-color
$nav-tabs-link-active-bg
$nav-tabs-link-active-border-color
$nav-tabs-border-width