The Van Buren Urethral Sound / Dilating Bougie (8 Charr, 27 cm / 10 ¾ inches) is a very thin, small-caliber urological instrument designed to carefully bypass and gently dilate highly restricted, narrow urethral strictures before larger sounds are introduced. [1]

The term "Charr" or "Charrière" is the historical and technical name for the French gauge (Fr) system.