CSS make flex wrapped elements not exceed their siblings width
<p>I'm stuck on problem with stretching flexes.
I have flexbox div with items. These items can stretch to full width and have min-width property, so that 3-4 elements can fit in large screens, and 1-2 in small.
I want to make their widths equal, but the problem is that wrapped items are wider if their quantity is less than on top elements.</p>

<p>Attached below my current result and expected behavior. How can I make it?
<a href="https://i.stack.imgur.com/YWf90.jpg" rel="noreferrer"><img src="https://i.stack.imgur.com/YWf90.jpg" alt="enter image description here"></a></p>

<p><div class="snippet" data-lang="js" data-hide="false" data-console="false" data-babel="false">
<div class="snippet-code">
<pre class="snippet-code-css lang-css prettyprint-override"><code>.items {
  display: flex;
  justify-content: center;
  flex-wrap: wrap;
  width: 100%;
}

.item {
  min-width: 400px;
  border: 1px solid black;
  margin: 0;
  height: 200px;
  flex-grow: 1;
}</code></pre>
<pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;div class="items"&gt;
  &lt;div class="item"&gt;1&lt;/div&gt;
  &lt;div class="item"&gt;1&lt;/div&gt;
  &lt;div class="item"&gt;1&lt;/div&gt;
  &lt;div class="item"&gt;1&lt;/div&gt;
  &lt;div class="item"&gt;1&lt;/div&gt;
&lt;/div&gt;</code></pre>
</div>
</div>
</p>

<p>Thanks!</p>

<hr>

<p><strong>Update 02.05.2016</strong></p>

<p>Thanks to @vals I came up with percentage width solution for different screen sizes. (But it seems I'm having some tiny problem with 33% width elements, in which 1% empty space is left around them xD)</p>

<p><div class="snippet" data-lang="js" data-hide="false" data-console="false" data-babel="false">
<div class="snippet-code">
<pre class="snippet-code-css lang-css prettyprint-override"><code>.items {
  display: flex;
  justify-content: center;
  flex-wrap: wrap;
  width: 100%;
  box-sizing: border-box;
  align-items: center;
}

@media only screen and (max-width: 820px)  {
  .item {
    width: 100%;
  }
}

@media only screen and (min-width: 821px) and (max-width: 1220px)  {
  .item {
    width: 50%;
  }
}

@media only screen and (min-width: 1221px) and (max-width: 1620px)  {
  .item {
    width: 33%;
  }
}

@media only screen and (min-width: 1621px) and (max-width: 2020px)  {
  .item {
    width: 25%;
  }
}

.item {
  box-sizing: border-box;
  border: 1px solid black;
  margin: 0;
  height: 200px;
}</code></pre>
<pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;div class="items"&gt;
  &lt;div class="item"&gt;1&lt;/div&gt;
  &lt;div class="item"&gt;1&lt;/div&gt;
  &lt;div class="item"&gt;1&lt;/div&gt;
  &lt;div class="item"&gt;1&lt;/div&gt;
  &lt;div class="item"&gt;1&lt;/div&gt;
&lt;/div&gt;</code></pre>
</div>
</div>
</p>