Performance wise it's more efficient using a base class (.glyphicon) and a modifier class (.glyphicon-adjust) instead of applying base styles with a pattern ([c

Performance wise it's more efficient using a base class (.glyphicon) and a modifier class (.glyphicon-adjust) instead of applying base styles with a pattern ([class^="icon-"]). Read about the other motivations for the change here: https://github.com/twbs/bootstrap/pull/6342 https://github.com/twbs/bootstrap/pull/6342