Caldwell E-Max Pro BT Alkaline Ear Muffs 24dB. These E-Max are Bluetooth compatible with mobile devices and have a 24dB noise reduction rating. With high quality stereo sound and easy to use push button volume controls you can listen to all your favorite music while on the range. Runs on (included) AAA batteries. Specifications for Caldwell E-Max Pro BT Alkaline Ear Muffs: Manufacturer: Caldwell Color: Black NRR: 24 dB Quantity: 1 Package Contents: Caldwell E-Max Pro BT Alkaline Ear Muffs Caldwell 1180978: E-Max Pro BT Alkaline Ear Muffs 24dB