These Pyrex® distilling suction tube adapters convert ordinary boiling flasks with 24/40 Standard Taper jointed necks to vacuum-type Standard Taper receivers. They have a 24/40 Standard Taper outer joint at the top and a 24/40 Standard Taper inner joint at the bottom. The sidearm is approximately 10mm O.D. by 25mm long. This tube is also a replacement part for organic chemistry kit no. 6949.