HUMI-SMART 2-way humidity control packs control moisture in an enclosed area. Our technology will either release or absorb moisture, maintaining relative humidity at 75% in a contained environment. We include a smart, simple-to-read to replacement indicator card with our HUMI-SMART packs. Simply replace the old pack with a fresh one when the dot on the replacement indicator card turns from pink to blue. The 300 Gram HUMI-SMART Two-Way Humidity Control is used to season humidors.