They are made of a type of mylar that withstands high heat. They do the job of keeping your slow cooker pretty cleans compared to scrubbing. It's a personal choice.
centurion12
Some slow cooker recipes say to grease the cooker before adding the ingredients. If you using a liner, do you still have to grease the liner or can you eliminate the greasing if using a liner. Thanks:chef:
centurion12