This scientific style bushing adaptor 19/14 is used to fit as perfectly so there is minimum air leakage.
Also known as low profile downstem due to when inserted in a piece it sits as flush as possible to the female ground joint.
outer diameter of bottom part of grounded joint: 19mm inner diameter of top part of grounded joint :
14mm diffussed slits on bottom
length size is determined by inches ( " ) from the bottom of the grounded joint to the end of the glass of diffussed area