The weight adjustable dumbbells come with an ergonomic design. They are durable and constructed from high grade nonslip neoprene ensuring safety while you exercise. They are multipurpose and can be used in a large variety of exercises. It features a simple design that makes adjusting the weights easy. The end of each dumbbell unscrews, you can insert or remove weight bars and then simply replace the screw cap back on. These dumbbells are to be used to increase muscle strength, provide resistance and add a challenge to every workout. They are the perfect way to stay in shape whether working out at home or in the gym. As with any new piece of exercise equipment, please consult with your physician if you have any underlying or preexisting health conditions.