where are $params located in Joomla

I am working on a Joomla site and I need to change one of the inline styles, located in the line below.

<ul class="menu" role="navigation" style="display: block; height: 50px; overflow-x: visible; overflow-y: visible; visibility: visible; ">

I've followed the style back to a module file where the corresponding line looks like this:

<ul class="menu<?php echo $params->get('class_sfx');?>"<?php
      $tag = '';
      if ($params->get('tag_id')!=NULL) {
            $tag = $params->get('tag_id').'';
            echo ' id="'.$tag.'"';
      }
?> role="navigation">

I think that the line  echo $params->get('class_sfx'); is inserting the styles, but am not sure. Is this correct? and if so where is the value of this variable stored so that I can change it?

Thanks for any help