metamask-extension/ui/components/component-library/modal-content/modal-content.scss

.mm-modal-content {
  position: fixed;
  left: 0;
  top: 0;
  z-index: $modal-z-index;
  overflow: auto;
  overscroll-behavior-y: none;

  &__dialog {
    --modal-content-size: var(--size, 360px);

    // Currently there is only use case size of ModalContent dialog in the extension
    // See audit https://www.figma.com/file/hxYqloYgmVcgsoiVqmGZ8K/Modal-Audit?node-id=481%3A244&t=XITeuRB1pRc09hiG-1
    // Not to say there won't be more in the future, but to prevent redundant code there is only one for now
    &--size-sm {
      --size: 360px;

      max-width: var(--modal-content-size);
    }

    position: relative;
    box-shadow: var(--shadow-size-lg) var(--color-shadow-default);
  }
}