Polar TechRB 15 RB15 Re-Freez-R-Brix Foam Refrigerant Pack, 4-1/2" Length x 4" Width x 1-1/2" Thick (Case of 6)

I've bought these twice and used them for shipping and also for air travel. Since it is like a brick when frozen, it's not an issue. It barely perspires so everything doesn't get all wet. They are reusable over and over again; 5 years and counting for the ones I haven't given away. It fit perfectly in the netted slot in my personal cooler which was a plus. And they are super useful to have in the freezer for power outages, but they can also be "thawed" and stored outside of the freezer if you don't have the space. If you need/want it to be in a square shape for shipping or tucking in a cooler pocket, I recommend freezing it flat. After freezing, you can store it upright for space saving.

Love these. They are definitely a foam brick, that upon freezeing develops a center bump. They have slightly more weight than most ice blocks, due to being bigger. Throw in the lunchbag, and goes 8 hours. These are bigger, and better, last longer to keep food cold. Ive been rotating 2-3 units daily thru the lunch bag cycle. They are durable, no holes after 3 months of daily use. They refreeze hard overnight, no issues. I expect these to last a couple years based on similar product experience in the past, and how they have done so far in 3 months. Great value. Buy, buy , buy.

We have used these cold packs multiple times now, and they have worked well for us through several freeze-thaw cycles. We are always careful where we place the freezer packs in the freezer and in containers to avoid poking holes in them. One hole and they are pretty much done.We have learned by experimentation that there is an optimal way to keep any food cold, or frozen, as the case may be. First, be sure the food container is insulated, and insulated well. Second, pre-cool the insulated container as much as possible. For frozen food, we pre-cool with dry ice if we can get some. Ice also works, but dry ice takes the pre-cooling to a much colder level. Third, remove all pre-cooling materials and remove any residual moisture. Fourth, fill the insulated container as much as possible. Fifth, add cold packs in any location where gaps or spaces remain. Since the cold packs are added last, the cold packs should be near the top of the insulated container so that the cooled air sinks from the top to the bottom. The advantage of the freezer packs is that they do not drip onto food as they thaw, assuming the packs have no holes!We have successfully shipped frozen food across the country (next day air) using insulated shipping containers with freezer packs and the food has arrived safely. We do not ship with dry ice because while dry ice is permitted on planes, dry ice requires "special handling," which means big dollars, so we stick to using dry ice for pre-cooling only, and pack as close as possible to the time of shipping.Admittedly, there are other options to using freezer packs. However, these are reusable and their rectangular ship is quite suitable for our shipping containers. Occasionally one develops a leak. We have not had any success in sealing a leaking freezer pack, so we dispose of those that leak. The other problem is getting the freezer packs back. Those we send locally we can usually retrieve. Those that go cross country become gifts to the recipient, which needs factored into the shipping cost. There are a few complaints about shipping costs, but generally most recipients are happy to have their food intact and edible and understand that the packaging does exactly that.Freezer packs meet a very specific need, and these are reusable, with care, and are reasonably priced. When used as part of a shipping process for cold or frozen food, they work great.Enjoy!

So the long story short is I had to send my serum and plasma overseas to the UK. The delivery was supposed to be within 48 hours and due to not one but TWO good ups from DHL it arrived in 96 hours so 4 days. I thought for sure we would need to go through the hassle again. But to our delight, the samples were at 6°c (42.8F) and it would be unacceptable if it was 8°C (46.4F) or higher.Thankfully the lab said they are 95% certain it won't be an issue and immediately sent my 30 0.5ml vials into a -80c (-112F) freezer.These things saved my ass and are AWESOME! Regular old supermarket freeze blocks definitely would not of held up in 80F+ weather for 4 days. Absolutely insane. Will always use these from now on.

I used these ice packs to keep food cold during a 6 hour flight and it worked great! In fact the ice packs stayed cold well past that. My only complaint is that the plastic packaging they come in isn't durable. They rip very easily so you have to put them in a ziplock bag as soon as you get them.

I flew from Jersey to FL using 5 of these, in two insulated bags in a checked suitcase, to keep homemade ice cream that I made to surprise someone frozen. When I arrived we had 7 hours of being out and about until our 3pm check-in. About 15 hours had passed when it was time to open it and one of the places we went let me put the bag in their freezer for an hour. I was scared to open the bag when it finally came time to reveal the surprise. It was a win! The ice-cream was still frozen!I do think the double insulated bag inside a suitcase helped for sure. Also because these are foam I didn't have to worry about a ton of water melting but there is naturally a bit on condensation but far less than ice.*IMPORTANT NOTE: Prior to purchasing these I noticed someone complained about how flimsy the bags were and that they tore. They are right! The plastic IS flimsy! So learning from their review I always keep each of them in their own closed ziplock back when I use them so I that the plastic always has a layer protecting it from tearing. WILL extend the life of these by a ton! I have never has to repurchase them. I even refreeze them in the ziplock. They basically live in their ziplock bags and from time to time I'll open them to clean them as needed.Since the ice cream mission I have also used them wonderfully to keep my lunch, such as salads, cool on a summers day and to keep groceries cool when I am not heading straight home. Definitely happy I bought these.