There are essentially 2 shapes of papers for use in a Chemex brewer ( AKA wood neck). There are the square filters or the Halfmoon papers, that require a little folding.
Both packs come in 100’s and can be used in all brewers. Both papers feel a bit like overkill in the 3 cup.
Original Chemex papers are chemical-free, ensuring no chemical residue. The thicker fiber filter design keeps the bitter elements, oils, and grounds in place and out of your cup.