.spinner-dual-ring:after {
  content: ' ';
  display: block;
  width: 2rem;
  height: 2rem;
  margin: 8px;
  border-radius: 50%;
  border: 3px solid;
  border-color: #3b99ef transparent #3b99ef transparent;
  animation: spinner-dual-ring 1.2s linear infinite;
}
.big-spinner:after {
  height: 5rem;
  width: 5rem;
}
.small-spinner:after {
  width: 1.25rem;
  height: 1.25rem;
}
@keyframes spinner-dual-ring {
  0% {
    transform: rotate(0deg);
  }
  100% {
    transform: rotate(360deg);
  }
}