R Lee Ermey from the History Channel show Lock & Load:

Making your own:

What I Did:
I started off with my favorite set of ear plugs The Com-fit AB corded ear plugs. DB 26 rating.

Then took my Px4 outside and fired 2 rounds into the hillside as to retrieve 2 spent .40 s&w casing (winchester 165 gr target ammo; 100 rnds $30 @ walmart). all my other brass i pawned at the gun shop for a few bucks.

Took a small nail; and hammer (because im too lazy to dig out my fathers reloading equipment) and gently taped, from the inside, removing the primer from both shells.

using a drill bit fed into the hole in the ear plug (ment for the cord) and put the ear plug into the casing, bit thru the primer hole, and filled it with hot glue from a glue gun. (WARNING CASING WILL BECOME HOT; use a vice or gloves when doing this step)

now on the .40 i had to drill the primer hole out a slight bit as it was too small for the cord to fit through. i then threaded the cord in thru the rear of the casing and viola…. spent casing ear plugs. novelty and hearing protection brought together as one.

Note: cord is NOT needed; but helpful to keep from loosing them. Also it helps secure the ear plug into the casing as it might slide back out after the glue settles (in testing it was rare but did happen; some super glue on top of this wouldn’t go amiss; however with the cord i don’t have that problem at all)

Source – mXm Community