#demo16{
  position: relative;
}
#demo16:after, #demo16:before {
  border: 10px solid transparent;
  border-left: 10px solid #fff;
  width: 0;
  height: 0;
  position: absolute;
  top: 0;
  right: -20px;
  content: ' '
}

#demo16:before {
  border-left-color: #f00;
  right: -21px;
}