I wanted to make something special for my wife for Christmas. Sure you can buy all kinds of wine bottle stoppers, but I wanted to give something of my own creation. I ordered both a Coral Red Strong & Flexible and a Violet Purple Strong & Flexiable. The Red definatly shows the details better in my opinion. If the bottle has just been poured they slide in very easily with a little wine lubrication. If the bottle is dry it is difficult to insert. Other materials have not been tested. They require an O-ring to seal. I purchased O-rings online from www.McMasterCarr.com part number 9396K208 (~$8 for 50pc). Silicone O-Ring 1/8" thick, 1/2" ID, 3/4" OD. If you are looking for something more personal, I also have a version with a suspended heart pendant inside that I can customize with your initials. Contact me if you are interested.