Urethral Sounds. The Hegar Sound Set is a urethral dilator sound set with a full set of 8 sounds. Each sound has a different sized end, thus the set offers sixteen sizes, ranging from 3mm to 19mm. The purpose of this sound set is to gradually and gently enlarge the urethra, when inserted into the urethra for such dilation. The sounds can also be used in other areas other than the urethra, such as anally, vaginally or prostate. Each set comes in a zippered velvet lined case for storage between each orgasmic session. Note these sounds are made from chrome plated brass. 3mm to 19mm e or approximately .11 inch to .74 inch.