The result of systematic research and development, the Dr. Perl junior System filter plus is a further improved version of the Dr. Perl junior activated carbon filter. A complex filter system has been developed to give the user extra filtration with low draw resistance, for an even more pleasant smoking experience. The different number of holes in the white and blue cap creates underpressure inside the filter, which results in greater swirling of the smoke. This more effectively uses the activated carbon and removes more harmful substances. Sleeve is made of white, chlorine-free bleached absorbent filter paper filled with flavorless activated carbon; this makes for cooler, drier smoking pleasure and considerably reduces nicotine and moisture levels in the tobacco smoke without affecting the tobacco's aroma. To ensure optimal function of the system filter, the filter must be inserted correctly: The blue cap must show toward the mouthpiece, and the white cap toward the bowl of the pipe. Treat yourself to maximum enjoyment and use a new filter, whenever you refill your pipe with tobacco. It's the only way to ensure optimal filtering of pipe smoke. Will fit all 9mm pipes.