I'm using mat-basic-chip with custom CSS, but I see a black border around the chip. any help is appreciated

The mat-chip has a funny black border on clicking. I'm not able to figure out what is creating the black border. here is the template and CSS

<mat-chip-list class="flex-full-width">
                      <ng-container *ngFor="let opt of question.options">
                        <mat-basic-chip #lbl="matChip" (click)="chipControlOnSelect(question.key,opt.key,fi,fgi, lbl)">
                          {{opt.value}}</mat-basic-chip>
                      </ng-container>
                    </mat-chip-list>

//style.scss
mat-basic-chip {
    display: inline-flex;
    padding: 7px 12px;
    align-items: center;
    cursor: pointer;
    border: 1px solid #9B9B9B;
    border-radius: 20px;
    opacity: 1;
    margin-left: 10px;
    font: Medium 14px/16px Roboto;
    &.mat-chip-selected {
        border: 1px solid $radio-yes-border-color;
        background-color: $radio-yes-background-color;
    }
    &:hover{
        background-color: $radio-yes-background-color;
    }
 }

I faced the same problem.

Just add in you css:

mat-chip-list:focus {
  outline: 0;
}

This will remove the black border