This creative use of inexpensive 3d-printing is so simple a 4yo can do it. Yet it amazes even adults.
If you don't have any 3d-printing experience, please sign up with Tinkercad.com first. You may be able to 3d-print your 3d model at your local library.
Step 1: Place Plastic Item in Hot to Boiling Water
The 3d-model of this bracelet can be built in any 3d-modeling program and from any overlapping shapes.
I used Tinkercad's "donuts," positioned them as a flat band, about 2x 7 inches, and 3-d printed it.
Now, put the flat band in hot water for a few minutes or more. (you can NOT over-do it)
Take it out and bend it to the size of your wrist. (it will cool quickly)
Step 2: Adjust to Any Size in Minutes
While it is soft you can bend it to the size of your wrist.
It even works with thermos-temp hot water.
Fun for the whole family!