I bought these canisters to make Alka Seltzer rockets with 7-10 year olds. The lids are very hard to take off and put on. The most of the older kids were able to do it themselves, but the younger kids needed adult help. We were able to make them launch into the air. It would have been nice if all of the kids were able to snap the lid on themselves. I have a couple of film canisters from back in the day when they were used for film. Those snap on very easily and are ideal for rockets. Anyone know where we can buy those?

I bought these to use for coffee while backpacking. One canister holds 1.5 tablespoons instant espresso, 1 teaspoon sugar and a pinch of salt, which makes a perfect (for me) 12 ounce cup of caffeinated heaven. I've also found them to be ideal for many other bits of gear. I have a small sewing kit in one, ibuprofen in another and also use them for spices and other dry ingredients. They are not reliably watertight, so not great for liquids.

The caps on all of them fit well and (for now at least) stay on securely. I have a bunch of old ones (that originally came with film in them) where the caps have worn a bit, so I expect the same with these when they get to be 10+ years old.

These worked great for our diet coke experiment!

The product included in the bag was exactly what I expected it to be and looks like it will do exactly what I wanted it for. Therefore, I gave the seller 5 stars as this is not their fault, unless Amazon was the seller. However, I have a complaint with Amazon on this one. I often purchase damaged packaged items to save a little money, especially when they tell you it is nothing but the package was damaged and the product is fine. Lately however, on items that contain multiple individual items like this, some of the product has been missing. In this case, I saved $1 by purchasing the damaged package, but since almost 1/3 of the product as missing, I ended up spending more per item than I would have had a purchased a non-damaged item. It feels like being ripped off because normally, these items would have been wholesaled out by the pallet load to other companies and sold off other people who sell on Ebay and such places. Amazon would have made only pennies on the dollar. As they are doing it, they got almost full retail, while I got ripped off. I will not bother with any damaged package items again. It simply is not worth it.

I teach a summer science class and have been using these clear Fuji film style film capsules for my Alka-seltzer rocket activity. These have worked great. The elementary students do sometimes have trouble removing the lids. However, you can't use the old style film capsules where the lid goes over the top. You need these kind where the lid sinks into the capsule and sits flush.

The lids do have grooves around the side similar to a quarter, which does provide some grip to remove it. So far, these capsules have worked great and provided a nice seal with which to conduct the experiment:

1/4 Alka-seltzer tablet
1/3 water (allowing room for the tablet to dissolve and create air pressure)
Flip it over with the lid down and stand back for it to launch. You'll sometimes still see some tablet residue as it may not fully dissolve before the air pressure causes the lid to pop--sending it flying up to 20-30ft high. :)