JSFiddle - React, Tailwind, and code Playground

HTML

<ul class="list-inner-border">
    <li><span></span></li>
    <li><span></span></li>
    <li><span></span></li>
</ul>

CSS

.list-inner-border {
    height: 100px;
}

.list-inner-border li {
    display: table-cell;
    position: relative;
    width: 1%;
}
.list-inner-border li + li:before {
    background-color: red;
    content: '';
    height: 80%;
    left: 0;
    margin-top: 5%;
    position: absolute;
    top: 0;
    width: 1px;
}

span {
    background-color: gray;
    display: block;
    height:90px;
    margin: 5px;
}