Knots are the only thing that lets these systems down. I've never seen a dark piece come back with well bleached knots. And usually most of the knots appear unbleached. It's very hard to bleach fabric dye out of processed hair, that's the problem. The best solution is to order a blonde front and color it to match yourself. I've done this for years and it works well. It's a bit more work when you get the piece but it's worth it to have no knots at the hairline.