From Chemex:

• Cone-shape ensures uniform extraction for pure coffee flavor
• Thicker (20-30% more than the competition) specialty fiber filter design keep bitter elements, oils, and grounds in their place (and out of your cup)
• Prefolded for convenience
• Will fit most other cone-shaped filter coffeemakers
• Fits all CHEMEX® Coffeemakers except CM-1, CM-1C, CM-1GH

We find that Chemex filters produce a very clean cup of coffee. They are suitable for when you would like coffee with a lighter body and no oils.