Round-bottom flask

Round-bottom flasks (round-bottomed flasks or RB flasks) are types of flasks having spherical bottoms used as laboratory glassware.

Round-bottom flasks and cork rings

Laboratory distillation set-up using a Liebig condenser, without a fractionating column. Both distilling (left) and receiving (right) flasks are round-bottom flasks.

They are used mostly for chemical or biochemical work. Today, they are usually made of heat-resistant borosilicate glass. There is at least one tubular section known as the neck with an opening at the tip. Two or three-necked flasks are made. Round bottom flasks come in many sizes.