The biggest problem with the 3M earplugs was they would not say in the soldier's ears. The Combat Arms earplugs would become loose because the basal edge of the third flange of the non-inserted end pressed against the soldier's ear canals. Then it would fold right back to its original shape. So the now loosened seal would cause the earplugs to fall out without the user even knowing.
Compounding that problem, the stem was too short which exacerbated the falling out problem.  So instead of reducing sound by the promised 25-40 decibels, it did not reduce the sound at all.