<p>Is either correct;</p><ul><li>Each class is for 5 minutes.</li><li>Each class is 5 minutes.</li></ul><br/><p>Both sound odd to me, and I edit them to be:</p><ul><li>Each class lasts for 5 minutes.</li><li>Each class is 5 minutes long.</li></ul><br/><p>Am I wrong?</p>