Expanding Diffuser will allow you to transform your 14.5 joint size bong into an 18.8 joint size. The male joint is 14.5, but the female joint is 18.8 to take 18.8 size bowls and accessories . These borosilicate glass downstems will act as adapters when you have differring joint sizes between your accessoriies and bong . They have hand firecut diffuser pin holes for strength and hand ground joints for a snug fit and the EDIT Logo , Available in various lengths