HYDROSORBENT® Silica Gel Moisture Absorbers for Camera (40gm - 1 Pack). Blue to Pink. Telescopes, Safe Dehumidifier Rechargeable. Reusable Desiccant Dehumidifier. Made in USA. 40g Mini Canister

Using them in my gun case. I have to re-charge these every few months. They seem to work quite well, though after going shooting on a rainy day, I still encountered some very light rusting the next time I took the gun out.Only caveat: I always have a hard time telling when the color has changed all the way, because I’m red-green colorblind, and the pink isn’t particularly obvious. (Though the pellets start out in a very dark color, I’m never sure whether they’ve turned color all the way yet.)

I have a bunch of these things. I use them mostly for moisture protection for firearms, since I live in very humid South Georgia. I have found that these 40 gram units work very well. I check the indicators on them frequently, and find that in summer they will need "recharging" about every two months, in winter only about every four months. This refers to items kept inside an air conditioned house. The recharge is really just drying the silica gel, done in an oven set at 300 degrees for 2-3 hours. No odor, so your wife won't get mad..I stick mine on a cookie sheet and let them bake while I do other chores. Good product, recommended..beware of some on the market that LOOK almost the same as these, but contain less gel, or crummy gel. The knock-offs are usually much lower-priced than these, but are a total rip-off.

I bought this to place in a small gun safe. I've dried it out several times now in the oven. It's worked perfectly preventing dampness and rust in my gun safe. Would be nice if you could put it in a microwave - but that is not possible, since it has a metal case. A better design would be plastic.

I purchased a waterproof/fireproof safe to store my valuable documents, however the safe mfg neglected to mention that within a few weeks my items would be hypersaturated from sitting in the safe. After sealing my documents in the safe I opened a few weeks later to notice that all the items were damp and had a dingy smell. I started doing some internet searches and found that many others have had the same issue. I decided to purhcase 2 of these 40 gram silica gel canisters. The items arrived promptly and looked just like the picture a metal canister with a viewing window to see the silica gel inside. I put it in the safe and after a few days the gel had gone from blue to pink. I expected this since one of the pages I read indicated that initally you would have to reactivate the gel often to purge the inital moisture. So I placed canister in oven per the instructions and they turned back to blue. I have only had the gel for a couple weeks but my documents have dried out and I have not noticed the moisture issue. These items are a life saver.

Only complaint is SHARP edges from stamping the case. They had to be filed down. Price was competitive. Hen Man.

Product had some nice reviews, so I purchased this one. However, after my purchase, I read some rather disturbing postings about this product. Based on those reviews, it was stated that this particular canister contained dangerous, cancer causing material, andthis could pose a real threat, especially when drying out in an oven for three hours. These warnings are a matter of open discussion in reviews, so I decided to throw out this product, and buy another with different material inside.

It is very similar to another 40 gram unit I got through Amazon. However this one has different color silica and a longer duration, higher temperature revive routine. That is surprising to me. So far both units seem to perform the same and at this point I would recommend them.

I had originally purchased several of the generic version, that says "Reactivate when green" [...] "280 degrees F" on the tin. The beads never really change color on those much, and I don't think they really work very well in the first placeBy contrast, these Hydrosorbent desiccants clearly turn pink when they need to be reactivated. I swapped out the generic ones in all my Pelican cases for these. I was surprised to see that they did their job far better than the generics, by orders of magnitude.In my case, I had a piece of equipment which was used for several hours during an overnight, and thus was exposed to a heavy dew. The following day, after opening the case I noticed a frost / fog inside the LCD display. Apparently the generic desiccant hadn't worked very well. I left the equipment in the sun to dry it out, which worked. I then ordered these Hydrosorbent desiccants to replace the generics, because I didn't have time to reactivate before I needed the same equipment for another overnight.First off, what seemed to be a dry case after an afternoon in the sun obviously wasn't. Lo and behold, the first Hydrosorbent went pink after a few days, before the second overnight. I replaced the first Hydrosorbent with a fresh one. After the second overnight, with similar dew conditions, there was no fog inside the display. That says it all!I don't know whether I should even bother reactivating the generics after this experience, but I definitely won't be buying more. I'm sticking with these.