7 mm is considered by many to be the ideal diameter. With it we developed the world’s first real activated charcoal joint filter and set standards for the imitators who would follow. Like its big brother, the 7 mm SLIM filter is well-filled and filters almost as well as our larger model. Nevertheless, it has a very handy size and therefore enjoys the greatest popularity among our filters. Like all actiTube products, it’s made in Germany.