I am autistic and I've had probably hundreds of fidget toys over my lifetime. This is, hands down, the absolute best type I've ever had. Simplistic in its design, the marble encased in crochet fabric is a silent, satisfying fidget used by sliding the marble around in the fabric.
Each fidget calls for less than 5 grams of fingering weight yarn and one flat bottom marble, though a standard round marble could be substituted.
The finished object is about 2 inches square, but size may vary depending on gauge. No gauge is given because it's irrelevant. As long as you get a fabric you like and the marble doesn't poke through, you're golden.