They are available in small and large sizes. If you feel no discomfort even if you put it in for more than 10 minutes, you can put on your underwear as it is and go about your daily life. The silicone is not as hard as plastic and has a gentle elasticity. There are five different sizes from no.1 to no.5. It is recommended that you start with a small size and gradually increase the size. This no.5 is about 25-28mm in diameter, 29mm at the root/135mm in length. Please refer to the photo that compares it to an AA battery. Each one is delivered in antibacterial packaging.