6 inchs diameter and round shape is big enough to fully cover small, medium, or large water drains. Round and flat bath tub drain plug creates strong suction to seal for the whole night without a large amount of water leakage. It doesn't move once sealed tightly in place. Easy to take off, convenient for storage when not in use. The Tub drain cover stopper is made of silicone. It won't harden and crack, soft, durable and flexible. Safe material won't hurt your kids, easy to care and clean. The bathtub water stopper can be used in your bathtub or kitchen sink to hold water, it blocks bad drain odor and seal out the smells from the kitchen sink, and even stops the tinies form crawling up the drainage pipes get into your house. Wildly applicable for most kitchen sinks, bathroom sinks, bath tube drains, and other drain strainer.