D'Addario Two-Way Humidification System

The Two-Way Humidification System from Planet Waves is a maintenance-free, two-way humidity control system which maintains the optimal 45-50% relative humidity level within your instrument case. Eliminate the guesswork and the potential mess related to refillable humidifiers. Unlike refillable units, the two-way system automatically adds or removes moisture on demand. The system ships with 3 Humidipaks and a soft mesh pouch that won't harm your instrument's finish. These packs will last from 2 to 6 months and once they become firm, simply replace with a set of replacement packs (available separately).