I have used quite a few different brands of purple shampoo, and as a hairdresser myself, find this to be the best one by far.
Sometimes, it can even be used on freshly bleached hair as a toner rather than applying another colour.
If it is used too much or left on a few minutes too long it can leave a bit of a purple hue behind which can easily be corrected by washing hair with a normal shampoo, but that aside, it definitely does its job well and at a reasonable price!
Ive been a bottle blonde for most of my life and my hair pulls a lot of orange when dyed. If the hairdresser dosen't tone enough I can always count on this to tone my hair perfectly. I also find freshening up between colours helps keep my hair bright and fresh
Tips: For some reason I find using a generous amount when my regrowth is hideous helps conceal it! Love using this to stretch out my appointments a few weeks