3M E-A-R ARC Plug 370-2000 Red/Yellow Universal Thermoplastic Elastomer Foam Reusable Uncorded Triple-Flange Ear Plugs -

Insert the red end: For continuous hazardous noise.
Insert the yellow end: For ambient noise levels that are not hazardous but arc potential is present.
The red earplug tip provides continuous noise reduction to surrounding sound.
Noise reduction with the yellow tip increases with sound levels for impulsive noise such as electric arc blast above 110dB.