These are my go to brand of desiccant for keeping my 3D printer filament dry. They work well and it is easy to tell when they need to be changed based on the color.When it comes to recharging them, you CAN use a microwave, but you have to do it slowly and repeatedly with the microwave on very low, otherwise the moisture all condenses inside the packs and just gets reabsorbed. If your oven has decent temperature regulation, it typically will work pretty well around 200F. I also have a food dehydrator that will go up to about 80C and it does ok if I leave them in it long enough, though we are talking HOURS here.That said, when it comes time to recharge them, I typically just cut the packs open and keep the beads loose, which makes them MUCH easier to get dried out in a bowl in the microwave. I then just add around a teaspoon or two to the bags I keep my filament in. You have to be a bit more careful when you get the filament out of the bags, but it really isn't that big a deal.Overall though, I highly recommend these.I bought these about 5 years ago, so let's start on that note.As far as their primary purpose of being a dessicant goes, these have worked out great. I've used them in gun cases, in storage with PLA, etc. And they've worked plenty well enough.Over the last several years I've just kinda let these packets saturate and then I swap them out with some new ones. Shout out to the bag these come in. Despite being 5 years old, the ones that have gone untouched in the bag are still blue. But with all that being said, I've recently taken it upon myself to recharge them now that I've saturated about 80% of these things. This task has been more difficult than I've thought.I've put them in the oven and forgot about them for a few hours, I've done the microwave method, etc. They always come off from heat as a deep blue, but within a few hours they're that pink/orange again.I can tell within the bag that there's moisture stuck. The clear window kinda fogs up. It almost seems to me that the moisture is unable to escape out of the packet, but that hardly makes sense, since the moisture had managed to get inside the packets.I've read a few people saying the microwave method is garbage, and to try the oven at 250. In the past I've had the oven set to 200 for a few hours, but I figure I'll give 3 hours at 250 a shot before I resort to just buying more. I'd update to 5 stars if I can manage to get these guys recharged. Otherwise 3 starts for being a perfectly adequate desiccant packet that doesn't recharge. For $10, it's gotten me about 5 years, so I'm not going to say it was a terrible, or even bad purchase, to begin with.Well this is a strange one ...I got these to replace the packs I have had for three years because they are weak after being recharged many times. Please refer to the picture attached - the old pack is on the left, new on the right. I was shocked when I inspected the new packs - they did not have any holes in them! The desiccant will not function if the outside air does not mingle with the desiccant (duh). All I saw were some sort of tiny scratches or areas where I think the "hole punching machine" would have made a hole. But there was no penetration at all.This is about the strangest product failure I've run across yet. How could they pass inspection like that? Just to make sure I wasn't misunderstanding a new desiccant technology I tested them in a bag with a pan of water overnight - nope they did not change color. I then got a sewing pin and punched my own holes and did the test again. Bingo they worked after that (go figure ...).And the label states "30+ years experience" I guess 30+ years isn't enough time to garner the right experience. If you but these get yourself a pin you'll need it. Rating a 2 for lack of quality control.There's nothing wrong with these silica gel packs. In fact, they work great. But for my purpose, I was looking to add them to a dry box where I store my 3D printing filament. It's more economical to buy the loose beads, same brand, Dry & Dry, than to use these packs. I thought it would be easier to recharge them in the packs but for the money, the quantity you get with the quart is best.I have two 5-quart dry boxes that have 2 lbs each in them. I wish I had bought the 5 lb instead of the 2 lb twice but I'll be buying more in the future. Keeps my dry box at 2-4% humidity so it works great.https://www.amazon.com/gp/product/B01I5Y2DG6/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1I bought these for my 3d printer filament storage box to keep the filament dry. Assuming the color change is accurate, they are doing their job of absorbing water. However, when they started to turn pink and I tried to recharge them, I discovered that they do not recharge well in the microwave. It does a nice job of removing the water from the silica, but that water just condenses on the inside of the packet where it gets immediately reabsorbed once you take them out of the microwave.Fortunately, they do recharge perfectly in the regular oven. I set mine to 215 degrees F (just above the boiling point of water) and put the packets in for 15 minutes. They came out as blue as the day I got them and there was no condensation so they stayed that way once they cooled off.I docked one star because they do claim you can recharge them in the microwave, which you really can't, and it will be somewhat annoying to have to heat up the oven each time I need to do a recharge. Otherwise they're a cheap way to keep stuff dry. If the microwave thing doesn't bother you, you'll be very happy with them.These come sealed in a bag and are blue when dry.After they absorb moisture, they turn pink.Simply put them in the oven for an hour and they can be used again.If you store ammo in a can in the original cardboard packaging, then these are what you put in your ammo cans to keep the ammo dry.