You just can't stay seated for a long time, here is your solution!

This round cushion has a slightly inflated inner tube that provides wavelike sensation to the person sitting on it.  This enables them to be more alert when performing tasks in a seated position. 

The round cushion comes in 2 sizes:  30 cm for children under 10 years old and 35 cm for children over 10 years old as well as teens and adults.