<div class="container">
  <div class="cus-select-group">
    <select name="" id="select-item">
        <option value="">Please select</option>
        <option value="">option 1</option>
        <option value="">option 2</option>
        <option value="">option 3</option>
    </select>
  </div>
</div>

#select-item{
  padding: 6px 0 6px 40px;
  -webkit-appearance:none;
  width:100%;
  border: 1px solid #c4c4c4;
  background-color: #f7f7f5;
}
.container{
  width:150px;
}
.cus-select-group{
  width:100%;
  position:relative;
}
.cus-select-group:not(*:root):after{
  content:"";
  display:block;
  width:0;
  height:0;
  border-color:#000 transparent transparent transparent;
  border-width:6px 3px 6px 3px;
  border-style:solid;
  position:absolute;
  right:6px;
  top:50%;
  margin-top:-2.5px;
}