Clarity™ filters out harmful noise while letting voices in. Patented technology offers sophisticated filtering without electronics. Blocks noise but helps wearer hear co-workers' speech, warning sounds and alarms. Vented headband and ear cushions deliver longwearing comfort. The dielectric design is safe for electrical environments. The C1 has a NRR of 20dB. The C2 has a NRR of 23dB. The C3 has a NRR of 27dB. Sold individually.