JSFiddle - React, Tailwind, and code Playground

HTML

<ul>
    <li><a href="">Link 1</a></li>
    <li><a href="">Link 2</a></li>
    <li><a href="">Link 3</a></li>
    <li><a href="">Link 4</a></li>
</ul>

CSS

ul {
    list-style: none;
    display: table;
    margin: 10% auto 0 auto;
    padding: 0;
    border-top: 1px solid #ccc;
    border-bottom: 5px solid #ccc;
    font: 1.3em/1.2 Arial, sans-serif;
}

ul:after {
    content: '';
    display: table;
    clear: both;
}

ul a {
    text-decoration: none;
    color: #000;
}

li {
    float: left;
    margin-right: 20px;
    padding: 10px 5px;
    position: relative;
    
}

li:last-child {
    margin-right: 0;
}

li:hover a {
    color: #ccc;
}

li:hover:after {
    content: '';
    position: absolute;
    bottom: 0%;
    border: 10px solid transparent;
    border-bottom: 10px solid #ccc;
    left: 50%;
    margin-left: -10px;
}