CanDo Large Cylindrical Gel Squeeze Ball Hand Exerciser, 6 Piece Set (Each: tan, yellow, red, green, blue, black) is designed for grip and strength, dexterity and mobility, as well as fine and gross motor skills. It can be heated or chilled for use in hot or cold therapy. Balls can withstand temperatures ranging from -76 degrees Fahrenheit to 167 degrees Fahrenheit.