My wife and I each got pairs of ESP electronic plugs in about 2000. We used to have a great bird dog and hunt birds 50 or more days per year. I used the ESPs for all field shooting for about a decade while the dog was alive. Had to get the body redone as the molded plastic failed on one after tons of use. It was covered on warranty. I still have the plugs, they still fit and work fine. I'd recommend them and they do amplify sounds like hearing aids if turned up. I'll list the issues with electronic hearing in the field:
1). Wind is a bugger.....I would leave the plugs in and just turn them off, otherwise they roar
2). It was hard to wear ear flappers for cold over them.......rubbed and made noise
3). You have to take the batteries out when storing for a longer period or they went dead, even if turned off. By removing the battery life seems to be great
4). The ESP units did not provide the protection of a good muff, so I quit using them at the range and just use regular muffs. This was especially noted when shooting trap next to a ported shotgun. Don't know the dB reduction they provide, but they seem adequate for shotgun use in the field where limited shots are fired versus sporting clays, etc.
5). I sold two O/U shotguns to fund the two pairs of ESPs. Good investment!
I don't even know if they are still in business....Broomfield, CO was their old location. Bet if they are the units are changed a bunch in 15 or so years. Anyway, mine still work.