An alternative to the Surprise Egg.
When kids start to get a little uppity, take 'em down a notch or two.
Also a US quarter fits in the opening if you really want to keep them on their toes.
Yolks, yellow change to black at 1.8 mm.
The magnet holes are for 0.25" by 0.06" (6.35 mm x 1.53 mm)