I have been using the Humidipak system since last year. Great product, as it keeps a constant humidity level inside my acoustic guitar case.
Just ordered this refill pack, so that I will have a replacement set, while the other recharges.
Haven't had any issues i.e. leaking or so. I recommend it.
Warning - as it is just a refill pack, it does not contain the pouches for the soundhole and neck area.