D'Addario Accessories Guitar Humidifier Packs - Two-Way Humidification System Conditioning Packets - For Maintaining Proper Guitar Humidification Level - 3 Maintain Replacement PacketsTWO WAY HUMIDITY CONTROL DAddario Two Way Humidification System is the only maintenance free two way humidity control system for guitar. It automatically maintains the optimal 45 50% relative humidity level within your instrument case by adding or depleting moisture as necessary. REPLACEMENT PACKETS Now available in 3 packs that are perfect for luthiers and guitar repair shops. On average, the packets will last 2 6 months depending on the geographic