CoffeeSock® ColdBrew filters are durable and may last a year or more. CoffeeSock® ColdBrew filters are a reusable alternative to paper filters and nylon sacks. All of our filters 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. CoffeeSock filters are made with Certified Organic Cotton. Cotton imparts no flavor on the finished brew unlike paper. Cotton is 90% cellulose, which is a tasteless and odorless compound that is insoluble in water. Wood is 40-50% while Hemp is approximately 45% cellulose.