[G2squared]

I have spend too much time shooting with standard military plugs and foam plugs due to "equipment restrictions". aka, this is what you're issued so it's what you'll use.
When I grew up and started shooting away from the military or with the AMU, I've always used a double plug setup. Early on it was foam plugs then custom silicone plugs with Dillion/Peltor electronic amplified muffs over them. The Dillon offering was the only ones that I felt had enough volume and fit well enough on my ears to offer additional protection and effectively amplify normal sounds so I could hear the things that mattered to me like normal conversation, range commands and people walking up behind me(not if they intended to be quiet, but normal walking).
I decided to get a pair of the TEP100s after seeing them at Shot Show one year and got the cased set that includes the charging waterproof case that protects and recharges the ear buds with a couple AA batteries. They came with several ear pieces, foam and silicone. The foam were advertised to do the most sound reduction and silicone a little less. They have 2 powered on volume settings, low and high.
So in practice I didn't like the fairly low rating of the ear buds alone. Sound amplification was great but it was a bit too much noise during shooting. Other machinery operation they have been great. I think for impact type noises then you would want more, like blacksmithing/hammering on steel and shooting.
Then I tried them under a set of regular muffs. I though it did effectively reduce noise and it was a great experiment in amplifying white noise. Sounded kinda like listening to a sea shell... didn't help hearing anything outside of the muffs. And if they are low profile muffs, then the ear bud will be pushed into your ear (potentially dangerously but at a minimum uncomfortably).
IMHO, it depends on what your intended use is, double plugging is a no go for me with these, but if you aren't up close to the shooting, they are great or if you are operating heavy machinery it's the perfect equipment. If shooting though, I still prefer an electronic muff over in ear plugs.

Mel

FWIW, Forgot to add that these will insert into the Surefire earpieces and other similarly sized plugs with holes in them so you're not stuck with just the ones Peltor makes.