JSFiddle - React, Tailwind, and code Playground

HTML

<ul>
    <li class="a">a</li>
    <li class="b">b</li>
    <li class="c">c</li>
    <li class="d">d</li>
</ul>

CSS

li.b {
    border:1pt solid black;
    width:10px;
}

li.c {
    border:1pt solid black; 
    width:10px;
}