Functions:(1) Insect prevention(2) Anti odor, deodorant(3) Anti defectionFeatures:(1) Easy to install, plug and play.(2) Fast drainage.(3) Adjustable Size.(4) Automatic opening when draining, closing after draining.Working Principle(1)When the water into the ground drain, the gravity of the water will open the bottom of the ABS gasket, dripping unimpeded.(2) After disruption of water, ASB gasket is automatically closed due to gravity.Completely sealed so that the gas in the pipeline, pests and over flow can not be up.Materical : ABS + MetalPS: Manual measurement may have 1-2mm errorApplications : for 3.5~4.5 cm holes