They change tone... in my case they made my slightly to mellow/warm strat even mellower, almost muddy, Nothing to complain about quality, they are softer steel than usual fender springs, so you need to use more of them, in my case all 5. They can be great if you need to tame harshness/brittleness or slightly soften attack, In my case I tried them and went back to original Fender springs.