They don't last. The color fades.
It looks good for about a week and then you have to pay through the nose to get it fixed. The guarantee is bull. A new "system" is thousands, and come from different suppliers whose quality varies widely. I wasted thousands.
Surgery is the only permanent, quality, convincing solution. Incorporation your own hair is a joke. They use it to "anchor your "rug," and it loosens as your hair grows and they charge you to "tighten' it back down. I threw thousands down the drain, and they never kept the color matched.
It rarely looked natural.