"Does a nice job - even in arid Colorado"
I am using one of these and one of the "bead" type jars in a fairly small humidor - probably 30 or so max capacity. This appears to provide the most stable level of humidity. It is very easy to use. Just keep fairly full with distilled water and the two jars combine to hold humidity just shy of 70%, even when humidity in the house is at or below 30%.
Jason in Colorado June 1, 2012