Adjusting width of dropdown menus

How do you make a specific dropdown item wider?   I would like to give the following its own width  <li><a href="#">Benefits</a></li>

<Div ID="Menu">

<ul>

  <li> <a href="#">Home</a></li>

<li>

   <a href="#">Products</a> See what we offer

<ul>

<li class="blue"> <a href="#">Portable Call Buttons</a></li>

<li><a href="#">Wall-mounted Transmitters    </a></li>

<li><a href="#">Pagers    </a></li>

<li><a href="#">Repeaters    </a></li>

</ul>

</li> 

  <li><a href="#">Benefits </a>

  <ul>

<li><a href="#">Benefits</a></li>

<li><a href="#">FAQs</a></li>

</ul>

  </li>

<li><a href="#">Our Customers</a>What & why they bought from us</li>

<li><a href="#">About US</a></li>

  <li><a href="#">Contact Us</a> </li>

</ul>

</Div>