These disc protectors fit over any 12cm optical media, forming a thin barrier protecting the shiny side. You can replace a damaged d_skin with a new one, but they don't protect the label side, where a scratch is usually more serious.
The skins didn't interfere with playback in our tests on a variety of PCs, DVD players and stereos. They fit snugly on to shop-bought DVDs, but could rotate around writable media. They protect against light scratches, but these can often be repaired by products such as Skip Doctor, which may prove more cost-effective.