<p dir="auto">Regarding the docs  components with property <code class="notranslate">mdDown</code>  should not be shown:</p>
<blockquote>
<p dir="auto">If true, screens this size and down will be hidden.</p>
</blockquote>
<ul class="contains-task-list">
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> I have searched the <a href="https://github.com/mui-org/material-ui/issues">issues</a> of this repository and believe that this is not a duplicate.</li>
</ul>
<p dir="auto">maybe related to <a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="257217280" data-permission-text="Title is private" data-url="https://github.com/mui/material-ui/issues/8172" data-hovercard-type="issue" data-hovercard-url="/mui/material-ui/issues/8172/hovercard" href="https://github.com/mui/material-ui/issues/8172">#8172</a> and <a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="226023868" data-permission-text="Title is private" data-url="https://github.com/mui/material-ui/issues/6767" data-hovercard-type="issue" data-hovercard-url="/mui/material-ui/issues/6767/hovercard" href="https://github.com/mui/material-ui/issues/6767">#6767</a></p>
<h2 dir="auto">Expected Behavior</h2>
<p dir="auto"><code class="notranslate">&lt;Hidden mdDown&gt;</code> components must not be displayed when <code class="notranslate">withStyles()</code> returns <code class="notranslate">width: "md"</code></p>
<h2 dir="auto">Current Behavior</h2>
<p dir="auto">Content is shown.<br>
Neither Safari's nor Chrome's "inspect" shows that the media query for class MuiHiddenCss-mdDown is matched.</p>
<h2 dir="auto">Steps to Reproduce (for bugs)</h2>
<p dir="auto"><a href="https://codesandbox.io/s/7wlyw4y8m0" rel="nofollow">https://codesandbox.io/s/7wlyw4y8m0</a></p>
<ol dir="auto">
<li>change window size in project view</li>
</ol>
<h2 dir="auto">Your Environment</h2>

<table role="table">
<thead>
<tr>
<th>Tech</th>
<th>Version</th>
</tr>
</thead>
<tbody>
<tr>
<td>Material-UI</td>
<td>1.0.0-beta.2</td>
</tr>
<tr>
<td>React</td>
<td>16.2.0</td>
</tr>
<tr>
<td>browser</td>
<td>Safari 11.0.1, Chrome 64.0.3278.0</td>
</tr>
</tbody>
</table>
<p dir="auto">If you confirm that this is a bug, please give me a hint where to fix it.</p>
<h2 dir="auto">Problem Description</h2>
<p dir="auto">Hi guys,</p>
<p dir="auto">I have been having performance issues that might be related to transition.js dependencies of material-ui.<br>
I have a medium size SPA using redux.<br>
I believe that one of the most CPU consuming process of my app are the ones related with material-ui components.<br>
I don't know if this is a fixable issue, but I'm attaching a snapshot of my chrome cpu profile.<br>
<a target="_blank" rel="noopener noreferrer nofollow" href="https://camo.githubusercontent.com/b6d06a8115a43b5157be54f86c169fcbac30ac4fac7c5d488402bebff93dd0aa/68747470733a2f2f646f63732e676f6f676c652e636f6d2f75633f61757468757365723d302669643d304233462d526e366250756e6257574a47636c46695a334e42516a51266578706f72743d646f776e6c6f6164"><img src="https://camo.githubusercontent.com/b6d06a8115a43b5157be54f86c169fcbac30ac4fac7c5d488402bebff93dd0aa/68747470733a2f2f646f63732e676f6f676c652e636f6d2f75633f61757468757365723d302669643d304233462d526e366250756e6257574a47636c46695a334e42516a51266578706f72743d646f776e6c6f6164" alt="Snapshot" data-canonical-src="https://docs.google.com/uc?authuser=0&amp;id=0B3F-Rn6bPunbWWJGclFiZ3NBQjQ&amp;export=download" style="max-width: 100%;"></a></p>
<h2 dir="auto">Versions</h2>
<ul dir="auto">
<li>Material-UI: "material-ui": "^0.15.0-alpha.2"</li>
<li>React: "react": "^0.14.8"</li>
<li>Browser: Chrome Version 49.0.2623.110 (64-bit)</li>
</ul>