Safety Structure: Double safety buckles on the tray and handle bar make this adjustable weight dumbbells can only be adjusted on the tray, the non-slip design at the handle ensures safety and stability during exercise after the dumbbell leave the tray. 1 Second Weight Change: Turn the handle with single hand to quickly adjust to the required weight from 4.5 lb to 22.5 lb. There will be a corresponding pointer and a click sound to let you know that the adjustment is complete, which is super easy to use.