We haven't tried them out yet, saving them for my son's birthday party on Sunday (we are doing them as an activity). I was opening them all up to assemble the molds and noticed I had 2 of the same piece so the mold is useless in one of the kits. Bummer because I have 12 kids coming to the party and only 11 working molds.Other than that, love the idea! Seems like a perfect little 'experiment' for a science themed party.

Very small...

So we got a bouncy ball kit and the boys loved them. I will say after about a week they turn rock hard. You’ll have to add a bit of water to make them rubbery again. Here’s a video we made of us doing the kit.DIY Bouncy Ball

We had fun making these (does require adult help for children 6 and under) but they dry out and are no longer bouncy soon after

We had a lot of fun following the instructions and creating the ball using the forms, however after about a day, the ball hardens so much that it doesn’t bounce anymore so feels pretty much like wasteful plastic use. So good for the “science experiment” but long term, you’re just making junk to throw away.