It is used in distillation to connect a round bottom flask and a condenser. The condenser and the round bottom flask connections are both male and has taper 24/29. The sidearm is angled at 75° for attaching a condenser.

In the taper symbol, the first number represents the outer diameter in millimeters at the widest point of the inner (male) joint and the second number represents the ground glass length of the joint in millimeters.

It also has a female taper joint 19/26 to accept separatory funnel or a thermometer via thermometer jacket or pocket adopter. It can be used with this Thermometer Jacket Adapter.

It is made form borosilicate glass and can withstand typical laboratory temperature variations. It is also called still head.