Use a chainstay protector when you want to protect your frame against nicks, scratches, and other damage that would be caused by your bike chain. Most chainstay protectors are made of some sort of plastic material, with the top side a smooth, slippery surface that your chain will easily bounce off of, and the underside coated with a glue substance for attaching to your chainstay. Most chainstay protectors are about 10 inches in length, though you can get shorter or longer depending on your bike configuration and geometry. Some chainstay protectors are made of a cloth-like material, but that tends to be old-school in design. When you have spent thousands of dollars on your bike, and you see that brand-new paint job perfect as can be, that's the time to buy a chainstay protector in order to keep your original bicycle paint job perfect. Generally, once you install a chainstay protector on your bike, it will last for the lifetime of your bicycle. However, they will get marked up over time, so you may want to replace your chainstay protector if it starts to look gnarly. If that's the case, be careful removing the old chainstay protector so that you don't pulll any paint off your bicycle. One of the top brands is Lizard Skins, which makes chainstay protectors in clear – so that you can see your original bike paint color – as well as a variety of colors. Also check out Lezyne , which makes high quality chainstay protectors as well.