What do the dB and NRR numbers on earplugs actually mean?

NRR (Noise Reduction Rating) and SNR (Single Number Rating) are lab-derived estimates of attenuation under ideal fit. Several listings here advertise very high figures (45dB, 50dB) that are physically implausible for passive earplugs and are not backed by independent testing in the supplied data, so treat headline numbers as marketing rather than guaranteed performance.