I bought these as I have a tendency to stand too close to the PA/Speakers at gigs, and I've also started playing in a band recently and didn't want to start having problems with my hearing - I'm not getting any younger!. I've found that these are very good in blocking both high and low end frequencies, which I guess is what they're supposed to do. But for me personally, they are blocking far too much of the sound, to the point now where I've stopped wearing them at gigs and practices. For an example, I recently put on a gig and stood in the middle of the (small) venue and listened to one of the bands soundcheck. I had to take the plugs out in order to hear properly and left them out for the rest of the gig. I also used them for the first time last week at a practice, but took them out after one song as even though I was standing within a few feet of my amp I couldn't hear anything unless I boosted the volume and gain to a ridiculous level. I found them reasonably comfortable but a little sore after a while, I bought medium but small might have been better for me. I don't know how to measure my ears!
Overall, I'm afraid I wouldn't recommend them, other than if you want something to almost completely block out the music. If I can afford it, I'll try something higher up the price range.