Uses:

Keyboard and mouse pillows designed for adults and children who spend long hours at the computer. The pillows conform to the shape of your hand and serve as an excellent work surface. When heated in the microwave for two minutes, pillows also provide a warm massage for painful wrists.
Size: keyboard - 50 x 10 cm; mouse - 17 x 15 cm

Notes:

Each microwave has a different power; hence a deviation from the above data might occur. 

In any case, please address your therapist for specific instructions for home usage.