Generated by SassMeister.com.

SassMeister-input-HTML.html

<div class="container">
<ul>
  <li>Test</li>  
  <li>Test 2</li>
  <li>Test 3</li>
</ul>
</div>

SassMeister-input.scss

// ----
// Sass (v3.3.14)
// Compass (v1.0.1)
// Susy (v2.1.3)
// ----

@import "susy";
$susy: (
    columns: 12,
    gutters: 1/3
);
.container {
  @include container(70.5em);
  background-color: lightgrey;
}
li {
 @include gallery(2 of 12); 
}

SassMeister-output.css

.container {
  max-width: 70.5em;
  margin-left: auto;
  margin-right: auto;
  background-color: lightgrey;
}
.container:after {
  content: " ";
  display: block;
  clear: both;
}

li {
  width: 14.89362%;
  float: left;
}
li:nth-child(6n + 1) {
  margin-left: 0;
  margin-right: -100%;
  clear: both;
  margin-left: 0;
}
li:nth-child(6n + 2) {
  margin-left: 17.02128%;
  margin-right: -100%;
  clear: none;
}
li:nth-child(6n + 3) {
  margin-left: 34.04255%;
  margin-right: -100%;
  clear: none;
}
li:nth-child(6n + 4) {
  margin-left: 51.06383%;
  margin-right: -100%;
  clear: none;
}
li:nth-child(6n + 5) {
  margin-left: 68.08511%;
  margin-right: -100%;
  clear: none;
}
li:nth-child(6n + 6) {
  margin-left: 85.10638%;
  margin-right: -100%;
  clear: none;
}

SassMeister-rendered.html

<div class="container">
<ul>
  <li>Test</li>  
  <li>Test 2</li>
  <li>Test 3</li>
</ul>
</div>