Howard Leight, QM24+, Earmuff, NRR 25, Red. 20 Pack Noise Reduction Rating 25 dB One Size Fits Most Can Be Worn in Multiple Positions These Earmuffs can be worn over-the-head, behind-the-head or under-the-chin. They feature Dialectic construction suitable for electrical environments and a Noise Reduction Rating (NRR) 25.