These Travel-Style CoffeeSock HotBrew filters are durable and made to fit self-contained containers. These filters are a reusable alternative to paper filters and nylon sacks and out-perform any comparable disposable and reusable filters. Cotton absorbs some of the oils released from coffee beans, yet lets acids pass through. The resulting cup is clear crisp, rich and robust with all the acid of paper brewed coffee, without the paper taste, and all of the richness of French press without the heavy oiliness.