Our Dumbbells are of solid construction and design with HEX lock collars and rubber covered weight plates to protect floors. They are made for gym & Home use, and designed so they can be adjusted for different exercises and different strength levels. The handles are constructed from solid steel with a life time structural warranty. We built to take it so you can expand your range and the intensity of exercises. Allows you to set 9 different increments of weight ranging for each dumbbell.