I love good finger toys at my desk to keep my ADD busy while I'm working. They need to be:

- Light: If they make a clanking noise every 5 seconds when you pick them up and put them down its just distracting.

- Plastic: There are other materials that work, but in general metals and fabrics react too strongly with your fingers over time, whereas plastic can be easily cleaned.

Having a little water window isn't a problem, but the water is also not as directly cool looking. Usually in the '90s you'd get those mixed color oil/water toys where the colors would make them stand out more, but shaking them would mix the substances causing them to lose function.

As such the electronic version is quite durable in comparison.