Pyramex 20 Sentinel Electronic Earmuff Nrr 26 Db Black Vgpme. The muff helps amplify hearing while compressing harmful sounds and reducing them to a safe level. It also has an auto shut-off after four hours 3.5 mm AUX jack for use of MP3 and mobile devices and height adjustment to fit all sizes. Specifications for Pyramex 20 Sentinel Electronic Earmuff Nrr 26 Db: Manufacturer: Pyramex Fabric/Material: Polymer NRR: 26 dB Quantity: 1 Battery Type: AAA Finish: Black