Tramec's Air Dryer Cartridges remove moisture and other contaminants from compressed air before it travels through system air tanks and valves. Featuring premium grade desiccant beads, oil filtering multi-stage media, and internal retaining springs all in a single drop-in unit, Tramec Oil-Coalescing AD-9 Style Air Dryer Cartridges prevent freeze-ups while extending component life span throughout your air brake system.