Like sunglasses for your ears!
These filters may not be enough for loud drummers or DJs sitting beside bass bins, but if you're a player who likes to still hear the monitors and feel present in the room, these filters are just right. They take a little bit of volume off, and don't isolate you as much as 15/25 db filters.
Worth buying a couple of sets at different strength. It would be good if they told you clearly what rating they were, especially clearly enough to be read in typical low-light gig conditions, if you keep a few different types.
I love my earplugs. Elacin ones do a much better job at cutting frequencies evenly than any other ones I've tried. Spend the money and do it right, musos. Your ears are too precious!