CALDWELL E Max Pro Ear Muff FDE 23NRR The Caldwell E-MAX PRO Ear Muff FDE 23NRR is a high quality bluetooth hearing protection with an all day comfortable fit at an affordable price. It is compatible with mobile devices and the low-profile design allows for uninterrupted cheek weld. They feature high quality stereo sound with 23dB noise reduction rating and easy-to-use push button volume controls.