D'Addario PW-HPRP-03 Humidipak System 3 Pack Refill
Refill for Planet Waves Humidipak system.
No upgrades available
Been using these for two years now on my two more expensive acoustic guitars. Recommended by my Guitar Engineer. They do exactly what they say and maintain humidity between 45-50%. You can’t just start using them from scratch - you need to get the humidity right by using the starter pack first. I guess it depends on local conditions but I seem to be getting 6-8 months use out of each refill.
Great refills for the D'addario 2 way Humidipak system