I've used those as well under a helmet as part of my gear. But the NRR of the ones I have used (22) is too low for me to consider them OK without doubling up. I didn't check but I think that is the best that you can get in this model. As I get older I really want to be able to hear later in life. If the solution doesn't at least get to an NRR of 30 I wouldn't recommend using it standalone.

I love my Peltor 500. Whatever you buy, upgrade to the gel cups. Just spent 4 hours with it on for my daughter’s pistol and rifle state match. I couldn’t do it without those gel cups.