Made of ABS plastic, copper and silicone.Each additional one scale, the pressure increases pound. The finger exerciser has a minimum pressure of 3 pound and a maximum of 8.5 pounds. Just one can meet your multiple needs, no longer need to spend more money.The 5-finger exerciser can help improve the strength and agility of hands and fingers, and is ideal for musicians.Specifications: Number of adjustable key pads: 5 Dimensions: 105 x 66 x 23 mm (4.13 x 2.60 x 0.91 inches) Net weight: 3.8oz/108g Tension range: 3Lb-8.5Lb,Rotate clockwise to increase strength,counterclockwise rotation reduces strength