metamask-extension/ui/components/app/gas-customization/gas-slider/index.scss

.gas-slider {
  position: relative;
  width: 322px;

  &__input {
    width: 322px;
    margin-left: -2px;
    z-index: 2;
  }

  input[type=range] {
    -webkit-appearance: none !important;
  }

  input[type=range]::-webkit-slider-thumb {
    -webkit-appearance: none !important;
    height: 34px;
    width: 34px;
    background-color: var(--color-primary-default);
    border-radius: 50%;
    position: relative;
    z-index: 10;
  }

  &__bar {
    height: 6px;
    width: 322px;
    background: var(--color-background-alternative);
    display: flex;
    justify-content: space-between;
    position: absolute;
    top: 16px;
    z-index: 0;
    border-radius: 4px;
  }

  &__colored {
    height: 6px;
    border-radius: 4px;
    margin-left: 102px;
    width: 322px;
    z-index: 1;
    background-color: var(--color-primary-muted);
  }

  &__labels {
    @include H7;

    display: flex;
    justify-content: space-between;
    margin-top: -6px;
    color: var(--color-text-alternative);
  }
}