This is the kind that you press down on to seal and press again to popup and unseal, correct? If so, it's a very common, reliable, simple design...no rocket science involved. I have a couple of them in my house and they work just fine. I prefer them to the more traditional kind that involve pulling up on a knob which is connected to a linkage which is connected to a lever in the drain pipe. And I've never had to adjust my pop down drains -- unlike those annoying lever-actuated ones.