Some hearing protection devices are marked red (right) and blue (left). If they are not marked, they are not side specific.
For custom products: Slide the thinner side into your ear canal and twist the plug until it fits comfortably in the ear. Pull up from the top of the ear, to straighten the ear canal, as you push the ear mold into the ear.
For non-custom products: Slide the thinner side into your ear canal and pull up from the top of the ear, to straighten the ear canal, as you push the ear plug into the ear. If you are using a foam plug, tightly squeeze and roll it before putting in the ear canal.