SOURCE

<div></div>

div{
    width: 80px;
    height: 30px;
    /* color: #FFF; */
    /* font-size: 1.2em; */
    /* text-align: center; */
    /* line-height: 30px; */
    background-color: #000;
    /* top:50%; */
    /* left: 50%; */
    /* margin-top: -15px; */
    /* margin-left: -50px; */
    position: relative;
}
div::after{
    content: "";   
    position: absolute;     
    width: 20px;
    height: 20px;
    top: 5px;
    right: -10px;
    /* display: block;  */
    background: #FFF;
    border-radius: 10px;
}