Little plastic ones maybe 1 or 2 millimeters with a flap on the end.
I believe the best way to protect your ear from getting water in it is to purchase moldable wax like ear plugs. It's cleaner and safer than cotton mixed with vaseline which may clog the tube and attract dirt in the ear canal. They are fine for swimming and showering.
I guess you are asking about the small plastic tubes inserted in the ear to drain them. My husband had to have one several years ago because there was so much fluid in the Eustachian tube. When you go swimming or shower, you have to put cotton in the ear and cover it with Vaseline so no water will get in. It gets messy. Many times these tubes will fall out on their own. Otherwise, they're left in for a couple of months at a time. They are very tiny tubes.
