25 ml conical tubes are designed so that professionals do not have to use larger tubes for small volumes. For example, it is no longer necessary to use a 50 ml Falcon tube for a 20 ml sample. These disposable tubes are made of transparent polypropylene and their ends are conical. They can be autoclaved and frozen. The lid of these tubes is screw type. Conical tubes are resistant to most common acids and chemicals in laboratories.