This glass on glass tobacco hookah downstem features a 19mm ground glass joint, is approximately 6" long (not including the joint), and the downstem portion is 16mm in diameter.
Please remember that ground joints are always measured as the diameter around the largest part of the ground portion. Male pieces are measured by the outside diameter and female pieces are measured by the inside diameter.
Please note that we do not have a picture of this model available so the shown picture is of the similar HKD12B.