JSFiddle - React, Tailwind, and code Playground

HTML

<div class = "box"></div>

CSS

.box {
    width:153px;
    height: 39px;
    border: 1px solid #cfcfcf;
    margin-top:50px;
    position:relative;
}

.box:before {
    position:absolute;
    content:'';
    width:0;
    height:0;
    top:-10px;
    left:50px;
    border-left:10px solid transparent;
    border-right:10px solid transparent;
    border-bottom:20px solid #cfcfcf;
}

.box:after {
    position:absolute;
    content:'';
    width:0;
    height:0;
    top:-8px;
    left:52px;
    border-left:8px solid transparent;
    border-right:8px solid transparent;
    border-bottom:18px solid white;
}