<div class="row">
<div class="small-12 columns">
<ul class="menu">
    <li class="li1"><a href="#">Home</a></li>
    <li class="li2"><a href="#">About</a></li>
    <a href="#"><li class="li3">Products</li></a>
    <a href="#"><li class="li4">Services</li></a>
    <a href="#"><li class="li5">Contact</li></a>
</ul>
</div>
</div>

li {
    display: inline;
}

.specific-li-class{
    display: inline;
}

<div class="row">
<div class="small-12 columns">
<ul class="menu">
    <li class="li1"><a href="#">Home</a></li>
    <li class="li2"><a href="#">About</a></li>
    <li class="li3"><a href="#">Products</a></li>
    <li class="li4"><a href="#">Services</a></li>
    <li class="li5"><a href="#">Contact</a></li>
</ul>
</div>
</div>

<div class="row">
<div class="small-12 columns">
<ul class="menu">
    <li class="li1"><a href="#">Home</a></li>
    <li class="li2"><a href="#">About</a></li>
    <li class="li3"><a href="#">Products</a></li>
    <li class="li4"><a href="#">Services</a></li>
    <li class="li5"><a href="#">Contact</a></li>
</ul>
</div>
</div>