These cloth-covered packets are the best. I use them to keep expensive machine tool parts dry and rust-free as well as my rifle and handgun ammunition dry.
These packets work great as long as they are used in a sealed container. They are not intended to keep things dry in an open-air environment. They are easily recharged in an oven (per instructions on the bag) so they can be used time and time again.
Make sure you buy the correct size for the amount of air space you intend to use them in (again, the bag lists those details). They work great!
Very good value! Product comes in sealed plastic bags that keep the product fresh and usable. I have not had to regenerate any packets and the bag reseals tightly.