GrowCNanswered grow question 4 years ago I love humidity packs and use Boveda brand. How many or how big you need depends on the size of pack, dryness of the product and the size of your container. The 8g packs are perfect for 20-30g that is already reasonably close on humidity and will last for many months. But, it you throw a pack into a big jar with a lot of bone dry it won't last as long as all that plant soaks up the moisture. 58% works but is a bit dryer than I like but the 62% are perfect.