Hegar Sounds are now available individually, for those who would like to try just one instead of purchasing a whole set. The Hegar Sound is a urethral dilator with each end a slightly different diameter. The purpose of the sound is to gradually and gently enlarge the urethra using a smooth metal shaft that is inserted into the penis. Urethral play can be an adventurous new facet of your medical fetish or BDSM scene. Measurements: 8.13 inches long, one end is 10 mm (0.45 inches) in diameter, opposite end is 9 mm (0.43 inches) in diameter Material: Chrome Plated Brass Please be well informed before you attempt this kind of play. It is very important that everything is sterilized and that you use a sterile water based lubricant.