Abstract: This invention provides an apparatus and method for an insertion medical device that dilates internal strictures. The insertion medical device includes a flexible dilator having an enclosed, hollow chamber substantially filled with crystalline tungsten powder. More particularly, a bougie is disclosed. The crystalline tungsten powder provides the bougie with improved flowability and performance when placing the bougie in the stricture. In another aspect, the invention provides improved flowability and adequate weight to other medical devices such as feeding tubes and endoscopy instruments.