The surfires appear to be aimed at the loud but not as loud as shooting racing noises. They rate race engines as 140dB while gun shots are usually over 160dB. These are probably similar to some musicians ear plugs that cut the noise down but still allow you to hear. They are not good enough for gunfire just trumpets.
Your friends 90 dB noise reduction claim is spurious, there is a limit due to bone conduction that limits any noise reduction focused on the ears to around 40dB
The only way to eliminate really loud noise and allow hearing is to use electronic muffs or plugs. There are some relatively cheap ($30) muff style ones out now, but the plug style electronic protection I have seen were pretty expensive. http://www.midwayusa.com/viewproduct...tnumber=774928