JSFiddle - React, Tailwind, and code Playground

HTML

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

CSS

.box {
    position:relative;
    display:block; margin:0; padding:0;
    width:100px; height:35px;
    background:#999; border:1px solid #444;
}

.box:before {
    position:absolute; content:'';
    display:block; margin:0; padding:0;
    width:100px; height:34px;
    border-top:1px solid #fff;
}

.box:after {
    position:absolute; content:'';
    display:block; margin:0; padding:0;
    width:100px; height:34px;
    border-bottom:1px solid #eaeaea;
}