STURDY CONSTRUCTION-FITSY adjustable dumbbells set is made from premium quality PVC with cement grit that is ultra-durable, environmental friendly nontoxic material and is resistant to chipping, crackling, peeling and waterproof, rustproof. Threaded ends with star-lock collars provide a safe, secure workout & easy weight plate changes . 2-IN-1 - With FITSY Extension Rod you can use this adjustable dumble set even as barbell dumbbell set rod for weightlifting, shoulder press, bench pres.