These paper microfilters were developed for the AeroPress XL coffee maker and are an essential part of every brewing process. They perform the same function as all coffee filters: They prevent coffee grounds from getting into the cup, ensuring a consistently grain-free cup of coffee.
They do this more reliably than most French press coffee makers, by the way. They're made of paper and are therefore biodegradable and compostable.
Only compatible with the AeroPress XL.