Green Filter 7129 Filter Green High Performance Air Filters are uniquely designed to take full advantage of cottons capabilities. Unlike multi-layer gauze filters which can fray and release fiber particles into your engine, Green Filter USA uses two layers of tightly interwoven cotton fabric. Cross weaving one fine, and one medium layer, produces a fabric that is thinner and stronger than other materials and has the ability to trap dirt up down to 5 microns.