Comfortable Protection from Hazardous Noise
The Howard Leight Sync Stereo Earmuff blocks noise in industrial or other environments with low to medium hazardous noise levels.
With an NRR (Noise Reduction Rating) of 25, the Sync provides consistent hearing protection, which means you'll enjoy a safe amount of attenuation even when you're surrounded by potentially harmful levels of noise.
Plug in and Go for Easy Operation
A standard 3.5-millimeter headphone jack allows Sync to be used with PCs and
portable audio devices.
The Sync is free of volume knobs, power switches, and batteries. Volume and power are controlled via your personal audio device, so all you have to do is plug in your device and listen.
I've seen a few youtube "fail" videos. Apparently these headphones may block the noise, but don't block the semi-trailer running you over when you don't have that situational-awareness