ROOR Gridded Classic Style downstem.
The joint is 18.8mm where the 16mm Duran Schott Glass diameter downstem meets the tube. The tip of the ROOR gridded downstem has a glass gridded base allowing more diffusion per hit. The Joint where the bowl is inserted measures 18.8mm and will fit with any 18.8mm male glass joint bowl all downstems are measured in ¼” inch increments from the bottom of joint.