Red pepper flakes, also called crushed red pepper, come from the cayenne pepper. A little fruity with big heat, you'll most likely encounter these kinds of flakes at your local pizza place or Italian restaurant, but they can go on anything. From vegetables to meat to eggs to sauces; anywhere you want some heat, sprinkle this stuff on.
 
Note about refill bags: 1x refill bag size is the same volume as a large jar. 2x refill bag size is double the volume of a large jar. 3x refill bag size is triple the volume of a large jar.