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 8 mm (0.315 inches) in diameter, opposite end is 7 mm (0.276 inches) in diameter, Material: Chrome Plated Brass