I use the packs to secure a toy box to send to my Daughter. They worked great! I used 16 of them for complete stability in the card board box I made out of a water heater box. They do initially get hot but are cool enough to touch in a few seconds. They will fill the outside wrap to about 1" thick when laid flat.

Works great! Make sure to always continue mixing up until the 2nd pop. It also sometimes helps to use the first second to spread out the material in the bag, but take too long doing that and that will ruin the attempt.

Basically if it is your first time using them, just accept that you will probably waste 1-3 while getting the hang of it.

Also ventilation is a must! Really don't want to breathe in the vapors! It messes up your throat and lungs. If you have trouble breathing after using one, take a break outside for a while.

I bought this size to fit ATX form factor PCs, and it works great. However, nowadays I'm primarily using it for PCs in Micro-ATX cases. It's a tight fit. If you're thinking about shipping mATX, tape some supplemental material (like air pillows that shipped with the components) under the metal lip of your case before inserting and expanding the foam to make sure the foam doesn't jam underneath the lip. If the foam expands underneath a lip or other obstruction and sets, the foam will be very difficult for your recipient to remove without breaking the foam and getting pieces of foam all over the insides of their new PC.

Beware: I had this foam break a panel in an mATX case because the foam expanded with too much pressure. Also, I had closed the panel such that the uninflated bag was partially hanging outside the case, so the closed panel blocked the steam vents.

This was all user error. Here is my advice:

Practice closing the panel before inflating. Pop and pat. Work quickly and carefully. Before the foam expands, make sure the entire uninflated bag is spread out inside the case (the steam should be able to escape from fan vents, for example). Attach the panel, close the panel, and push against the panel firmly with your hands to reinforce the panel and ensure the expansion pressure doesn't break the panel fittings. When the foam finishes expanding, the pressure will equalize and you won't have to reinforce the panel any more. I've shipped several PC's across the US with this foam and they've always arrived in perfect condition. Good luck!

These are great for packing but using two will cost you $8 - not an issue if you are packing high-dollar merchandise but anything normal and it becomes too expensive to use.

Bought a box of these to use with my ebay shipping. Much more secure than using air pillows, especially when the item might pop those or not stay secure.
I recommend test fitting the item and make a plan as these balloon faster than you expect.
Crack the vials, play some patty cake, stick them in place, and away they go. I find closing the box ASAP helps fill fit it all into place. Foam is soft enough to easily remove, but sturdy enough I don't really worry about the contents, though nothing is 100% given a determined delivery driver.
The cost to me is worth it as it saves time and lets me maintain my air pillow stash (thanks Amazon) for items that don't need this level of protection. Just one or two strategically placed packs will keep most items locked into place for safe shipping.