Selectors Hell

<header class='header'>
  <div class="inner">
    <div class="buttons">
        <button class="products"></button>
        <button class="services"></button>
        <button class="cool"></button>
        <div class="header_panel"></div> <!-- has child main-panel-item of main-panel -->
        <div class="header_panel">
          <ul class="header_main-panel">
            <li class="header_main-panel-item"></li>
            <li class="header_main-panel-item"></li>
            <li class="header_main-panel-item"></li>
            <li class="header_main-panel-item"></li>
            <li class="header_main-panel-item"></li>
            <li class="header_main-panel-item"></li> <!-- the one i want to apply styles-->
          </ul
        </div>
        <div class="header_panel"></div> <!-- has child main-panel-item of main-panel -->
    </div>
  </div>
</header>