Boveda is easy-to-use, maintenance-free humidity control for wood instruments-fretted, bowed and woodwinds. Keeps an instrument humidified and dehumidified-whatever its surroundings call for. This product is a replacement Boveda for use in Boveda fabric holders (included in the Boveda Starter Kit and sold separately). Stop adding water to foam, hoses and sponges in your instrument case. 1-way humidifiers require CONSTANT ATTENTION AND COULD DAMAGE AN INSTRUMENT, affect the sound and playability and lead to costly repairs. Boveda is easy-to-use, maintenance-free humidity control for wood instruments-fretted, bowed and woodwinds. Keeps an instrument humidified and dehumidified-whatever its surroundings call for. Just slip Boveda into Boveda fabric holders. Then nestle in and/or around the instrument. Close the case, then Boveda automatically adds and/or absorbs moisture all around a wood instrument. Achieves and maintains a constant relative humidity (RH) range of 45% to 55%-the safe zone for wood instruments. Uses only pure water and natural salts sealed inside a leakproof membrane. 49% RH Size 70 is recommended for use in most 3- or 4-season climates. Provides humidity control for 2 to 6 months based on the instrument case, time of year and climate. A simple touch test will let you know when it?s time to replace Boveda-it will feel crunchy and rigid. Note: ALWAYS insert Boveda into a sleeve of a Boveda fabric holder before placing in an instrument case. Do not mix different Boveda RH levels within the same instrument case. And do not use Boveda in the same case with other humidification products because they will fight against each other and reduce the efficiency of Boveda.