chosen.claro.css in Chosen 3.0.x        
                          
                  
                        
  
  .form-element.chosen-container-single {
  width: auto !important;
  padding: 0;
}
.form-element.chosen-container-single .chosen-single {
  min-width: 160px;
  background: none;
  border: none;
  box-shadow: none;
  width: 100%;
  height: 100%;
  display: block;
  line-height: 1.5rem;
  padding: calc(0.75rem - 1px) calc(1rem - 1px);
}
.form-element.chosen-container-single .chosen-single b {
  background: none !important;
}
.form-element.chosen-container-multi {
  width: auto !important;
}
.form-element.chosen-container-multi .chosen-choices {
  min-width: 160px;
  border: 0 none;
  background: none;
  box-shadow: none;
}
.chosen-container-active.chosen-with-drop .chosen-single {
  background: none !important;
  border: 0 none !important;
}
 
  
  
File
  css/chosen.claro.css
  
    View source  
  - .form-element.chosen-container-single {
 -   width: auto !important;
 -   padding: 0;
 - }
 - 
 - .form-element.chosen-container-single .chosen-single {
 -   min-width: 160px;
 -   background: none;
 -   border: none;
 -   box-shadow: none;
 -   width: 100%;
 -   height: 100%;
 -   display: block;
 -   line-height: 1.5rem;
 -   padding: calc(0.75rem - 1px) calc(1rem - 1px);
 - }
 - 
 - .form-element.chosen-container-single .chosen-single b {
 -   background: none !important;
 - }
 - 
 - .form-element.chosen-container-multi {
 -   width: auto !important;
 - }
 - 
 - .form-element.chosen-container-multi .chosen-choices {
 -   min-width: 160px;
 -   border: 0 none;
 -   background: none;
 -   box-shadow: none;
 - }
 - 
 - .chosen-container-active.chosen-with-drop .chosen-single {
 -   background: none !important;
 -   border: 0 none !important;
 - }