model:s-yy-ft-4217 this kind of product is suitable for one-piece toilet. the flushing volume is controlled by the length of the time a user presses on the button. under normal water pressure, when the user presses the button for 1.5-2.5 seconds, the water tank will be set to flush in heavy mode and discharge all water in the tank. and if the button is only pressed for 1-1.5 seconds, the water tank will be set to flush in light mode and only half a tank of water will be discharged.