Dry-Pac Refill, Color Changing For Air Venturi/Hill hand pumps that have a Dry-Pac unit Also compatible with Dry-Pac Pro Air Dryer Filter New color changing media for the Dry Pac (color changing moisture saturation indicator beads) Removes 90% of harmful moisture Replace every 4 months (every 2-3 months in warmer or more humid climates) Non-toxic Dry-Pac desiccant only Includes 2 refill packs Keep moisture out of your gun's air reservoir! Moisture causes rust and can compromise the integrity of your tank. This is the medium that's inside the Dry-Pac unit. These Non-Toxic refills remove 90% of harmful moisture. Replace each filter every 4 months (or 2-3 in humid climates).