The industry leader in 2-way humidity control, Boveda Packs are formulated to provide specific humidity levels. These can be used anywhere in your humidor and the slim design means they won't crowd out your cigars. It is recommended you use 2 packs for every 50 cigars. Do not use packs with different humidity levels or they will work against each other. Example: don't use packs at 72% with packs formulated at 65% at the same time in your humidor. Each pack usually lasts 2 months and should be replaced when they feel dry and rigid. Dimensions: 5.2" x 3.5"