Convenience, affordability, meets a product that just works
Let's begin with the most important thing to know about this product, each "core" displaces 8 ounces of liquid. This means, if placed in a 40 ounce bottle, you will have 32 ounces of actual liquid. If placed in a 64 ounce bottle, you will have 56 ounces of liquid.Because of this, I recommend using this product with a bottle of a minimum of 40 ounces, if not 64 ounces. Anything smaller would not make alot of sense (sticking one in a 20 ounce bottle would only leave you with 12 ounces of liquid left).The product takes approximately 4 hours to freeze. These are sealed exceptionally well, they will not leak, it is sonically sealed with no gaps.They are stainless steel with a water filled internal, which you can hear if you shake near your ear when the device is thawed.This gives you the best of both worlds, the benefits and thermal properties of water / ice (which are far better than stainless steel) while providing the benefits of stainless steel (which I will cover shortly). There is a very effective balance made here between stainless steel and ice, and this unique product, of which I have been unable to find anything like, but of which I have searched for years, finally exists in this product.So how does it work? It comes with two cores in a cardboard box. It is very easy to open, literally seconds to take out of the packaging, wash, and stick in the freezer to start freezing.I literally put them in the door of the freezer and after four hours, grabbed one and placed it in a 64 ounce insulated bottle, filled the bottle with already refrigerated water from a refrigerator set to 36 degrees. The liquid stayed cold for easily 24 hours, and I would argue, 36 hours later was still icy cold. Nothing outside of the core and the refrigerated water was added.When we are talking about the efficacy of this product, two things are critical. First, you should use already refrigerated liquid because of the thermal properties of stainless steel. Without getting into the physics, stainless steel becomes significantly less effective when it is used to bring the temperature down vs maintaining already cooled liquid. In short, the heat transfer from or to stainless steel is not efficient at all. If stainless steel is not in near equilibrium with the liquid it is placed in, it will transfer and loose much of its available energy equalizing the temperature. You can think of this like a car. Accelerating to a certain speed uses significantly more fuel than maintaining that same speed for the same duration it took to accelerate. This is where ice shines. If you have liquid that is room temperature or warmer, you should use ice to lower the temperature than these cores. They will be far less efficient otherwise.The second critical part to this equation is your bottle choice. There are a number of very good choices, in my testing of bottles, some of the most effective bottles are the Yeti 40 ounce rumbler (with exception to the lid design, which has no insulation, in a situation where the bottle may tip and liquid coming in contact with the lid, the liquid will warm very quickly). Hydroflask is also relatively decent, not the best performing, but works very well, with a similar issue to the aforementioned Yeti lid, although not as extreme. The third option I highly recommend is the "Coldest" bottle, either the 46 oz or 64 oz option if using these cores. Coldest performs identically to the other two I mentioned except, where it wins is, the lids are insulated. It doesnt matter if the lid comes in contact with the liquid. The lids are also much better designed and much more interesting and unique bottle art designs, I do wish they didnt have the insane branding on the bottle, but I digress. If you are looking for an affordable option that is easily available, look into the brand RTIC, generally half the price of the other brands I mentioned above and perform just as well, again, with exception to the lid insulation issue.Yes, Ive used this for ice water, tea (sweet and unsweet), lemonade, etc. It merely required rinsing off with tap water and placing in the freezer (no need to dry off, just stick it in the freezer).Pros- Ease of use, take out of bottle, rinse / wash, stick in freezer, place new one in bottle, dont have to spend time scooping / collecting / making ice and potentially dropping ice on the floor. Extremely fast and easy.- Does not water your liquid down.- Lasts 24-36 hours.- Inexpensive. This product is very affordable in my opinion.- Quick to freeze (3-4 hours to make ready to use).- Does not alter the taste of the liquid you put it in.Cons- Should not be used to cool liquid, it should be used with liquid that is already just above freezing temperature.