As a musician, singer, sound engineer etc its very important to keep your ears protected, so I decided to invest in some ear plugs.
These are a cheap and cheerful way to do it, but there are some major drawbacks unfortunately.
When singing with these in I found I had almost no control over the mic, as I could hardly hear anything I sang. Therefore they unfortunately block out too much sound to be used for singing.
They also don't fit everyone's ears. They fit mine fine and I can wear them for hours without too much ear ache, but my girlfriend couldn't even get them in her ears. Since they are a 1 fit design that's a big flaw.
Conclusion:
These work very well to protect your ears, a little too well though, so if you're singing you will have a lot of trouble with these. If you are just a musician or want something to protect your ears at concerts this will definitely do the trick. I always carry these plugs on me and put them in my ears before and after doing gigs so I can give my ears a rest after performing.