The Boveda Humidifier 320 Gram Pack of 6 is the most versatile humidifier you may ever use. Each 320-gram pack is designed to keep your humidor at its optimal RH levels, and virtually maintenance free. For wood humidors, one pack will last 2-4 months. For airtight humidors such as tupperdors, each pack will last 6-9 months. Plus, each pack is individually wrapped in a factory sealed high-barrier plastic, which if left unopened has a two-year shelf life.