Flat tires. They happen to everyone, despite tire technologies progressing over the years, and there are ways to help prevent them and keep them at bay in many situations. Tubeless tire set-ups with your choice of sealant the most common set-up and preventative measure but in the last couple of years, tire liners such as CushCore, Flat Tire Defender, and Huck Norris, among others have become increasingly popular in adding an extra level of protection against flats.
There are a number of systems available now, each claiming their own benefits over the other, but they're similar conceptually. The foam liners further protect the wheel and tire from damaging impacts. They also allow the rider to run a lower air pressure without as great of a chance of rolling the tire off the rim and also giving some extra cushion against rim and tire damaging impacts that may occur. There are a number of other benefits people will claim ranging from increased vibration damping properties to being able to ride out a flat, but, that's the main idea.
Whether these foam liners actually provide that much more protection and make a difference that's worth the frustration of installation and the associated weight penalty is heavily debated among riders—not to mention their price. I'd wager that there's a pretty mixed spread of people who do and don't use them. It does, however, seem that foam liners have progressed beyond the point of being considered a gimmick and there are some real benefits they can offer in a number of situations.
What are your thoughts on tire inserts? Do you use them? Want to? Have no desire to? Tried them and hate them? Couldn't even get them set up? Let's hear it.