The Hegar urethral sounds set gives the widest range of dialation, from approximatly 1/16" up to 3/4". The sounds are hollow which makes them lighter. Some people prefer this as body movements will cause the sound to vibrate less when inserted. Sounds come in various styles, as listed below. This is probably the second most common set of sounds we sell ( with Pratt being the most common ). Hegar is the style, it is not a brand name. These are for use by trained people. We suggest that you make sure you know what you are doing before using any style of sounds.