.select_box{
  width: 200px;
  overflow: hidden;
  border: 1px solid #000;
  position: relative;
  padding: 10px 0;
}
.select_box:after{
  width: 0; 
  height: 0; 
  border-left: 6px solid transparent;
  border-right: 6px solid transparent;
  border-top: 6px solid #f00;
  position: absolute;
  top: 40%;
  right: 5px;
  content: "";
  z-index: 98;
 }
.select_box select{
  width: 220px;
  border: 0;
  position: relative;
  z-index: 99;
  background: none;
}