Leave nothing to chance. Add precision to your lectures on the gas laws. This unit works by pressurizing a vessel to displace a small amount of water. The pressure can be ready with the included gauge to determine the volume of air and water, it is possible to calculate air volume. Our economical design has a flexible tube connected to a gauge, a glass vessel to hold water, a glass tube for containing displaced water and a meterstick mounted to a sturdy base. Instructions included.