Guys as i posted i did think about this and I ducked off and did some research and checked the packaging on the ones I have and it says 'hearing protection for up to 110db', and when I looked up the product in more detail I could see it was only 27db reduction
ProBell Disposable Uncorded Earplugs - EPYU - Earplugs - Hearing Protection
Did some more research into some other plugs I have used in the past and found them all to be similarly rated.
HOWEVER it's the frequency of noise that they block that seems to be the defining factor - I used a similar plug last week that higher rated (32db) and was pretty ineffective but it was a 'snore blocker', whereas the ones I bought that were 27db were industrial so perhaps they are designed to block differe t frequencies. I prefer the industrial ones because they block out the mechanical chatter but also retain some of the bass but without being 'boomy'.
Reality is that personal preference will define which plugs work best for you so you'll probably need to try a few. The basic disposable ones do the job really well if you find the right brand for you, and you can buy in bulk!
As an aside I spent $165 on a custom fit lab produced pair and they were crap compared to these $0.95 plugs.
Sorry for the bum steer at the beginning of the thread.