Model SG31 has noise reduction rating of 31 dB, weighs 2 oz, and is designed for user comfort. Offering consistent protection without distortion across all frequencies, ZEM technology uses mechanical energy of sound waves to minimize sound. Wearer is fully protected from harmful noise but can still discern speech and other ambient sounds. No batteries are required. Model SG26, with noise reduction rating of 26 dB, is also available.