These Claisen adapters have a standard taper outer joint at the top of the main tube for use with jointed thermometers. The 10/18 size is used with 10/18, 25 mm immersion thermometers while the 10/30 is for use with 10/30, 75 mm immersion thermometers. The sidearm has a standard taper outer joint with the main tube having an inner joint of the same size. These adapters are typically used in distillation setups.
These adapters are available in three different joint configurations.
For Claisen adapters with all three joints the same size, see item # CG-1020.