For the first time, the D'Addario Two-Way Humidification System (formerly Humidipak) is now available in bulk 12 packs. This is the perfect solution for luthiers and guitar repair shops. The Two-Way Humidification System is the first maintenance free, humidity control system, made by Boveda, which preserves a constant 45%-50% relative humidity level within your instrument's case. This eliminates all maintenance and guesswork.