The winding knob (the crown) has a gasket inside that fits snugly over the post (the stem) and creates a water resistant seal to prevent dust and water from entering the Eco-Drive watch. It takes very little water inside a watch to rust and damage the movement (watch mechanism). We recommend you have the stem and crown for your Eco-Drive watch replaced as soon as possible.
Tags: Citizen Eco-Drive, Stem and Crown