The T3H Cap Mount Thunder® Earmuff offers top-of-the-line protection and comfort. The dielectric construction is suitable for all workplaces, especially electrical environments. This muff can be used with a wide range of popular hard hats. The earcups snap in place during use and swing back when not in use. An adapter is included. The T3H Cap Mount Thunder® Earmuff has a NRR rating of 27.. Sold in a case of 10 earmuffs.