California Faucets’ ZeroDrain is a “pop-down” drain that sits flush with the sink and requires no lift knob to operate it. A one-finger touch is all that is needed to pop-down the stopper into the closed position and allow water to fill the sink. It features a piston design for a perfect seal every time. Press the stopper again to release it and water will disappear into the thin circular gap around the stopper. Pull out the stopper, rinse and reinsert for easy cleaning.