[Environmentally Friendly Silicone Material] - The hand exercise rings are made of premium silicone, suitable for smooshing, squeezing, stretching and pulling with no odor, no stains, no edges, no noise. It will immediately return to its original shape [5 resistance levels] - Yellow-20LB/9KG; Green-30LB/14KG; Blue-40LB/18KG; Orange-50LB/23KG; Black-60LB/27KG.Work out in different ways with multiple options, from beginner to advanced, at home or in the gym. [Great for rehabilitation, fitness and relaxation] - It can improve strengthening and dexterity of your fingers, more musculature of the forearm. So it is training for rehabilitation, long-time typing. Ideal for athletes (tennis, basketball, boxing, crossfit, golf and shooting) and musicians (guitarists, bassists, pianists and violinists) . [Easy to use and portable] - Exercise your hand and forearm anywhere, whether you are at home, at work, walking, in the car or doing your favorite sport as the rings are lightweight and easily portable. [Sized for a perfect and comfortable fit] - Sized specifically for adult hands, unlike other brands, to maximize the benefits of exercise and ensure a stimulating yet safe experience . Ideal for strong men or women.