Official Chemex bonded paper filters in the white square fold, 100 to a box. They are noticeably heavier than a standard cone filter, and that thickness is the whole point: it holds back the oils and fine particles that would otherwise cloud the cup, which is what gives Chemex coffee its unusually clean, almost tea-like clarity.
To use, open one filter into a cone with three layers on one side and a single layer on the other, seat it in the brewer with the three-layer side against the pouring spout, and rinse it through with hot water before you add coffee.
