Two of these packets will keep a 50-count humidor at the stated RH for three months with no maintainence whatsoever. They're sold in 65%, 69%, 72% and higher levels (I don't think anyone would want the 84% packet in a humi). I've been using them for about a month now and am very pleased with the results. There's no worry about filling a credo and the packets can lie right on top of the smokes if need be.