Example
text_letterSpacingNormal
text_letterSpacingLoose
text_letterSpacingLooser
text_letterSpacingLoosest
Markup
  <span class="text_letterSpacingNormal">text_letterSpacingNormal</span><br/>
  <span class="text_letterSpacingLoose">text_letterSpacingLoose</span><br/>
  <span class="text_letterSpacingLooser">text_letterSpacingLooser</span><br/>
  <span class="text_letterSpacingLoosest">text_letterSpacingLoosest</span>
Source: text/fonts.less, line 28