The apparatus consists of a horizontally mounted acrylic tube with a graduated scale along one side (scale graduated from 0 to 270cm³). The tube unit is sealed by a standard gas tap next to which is mounted a standard pressure gauge. The effective length of the tube is controlled by altering the position of a rubber stopper which is moved via a screw thread. Users can select the effective length of the tube by positioning the stopper and closing the gas tap. The volume of the tube can be read off the scale and printed against the corresponding pressure taken from the gauge. By varying the position of the stopper Boyle's Law can be investigated.

• This unit has the advantage over the standard model as it does not require oil to indicate the volume of air.
• The tube is made out of acrylic which is known to fail 'safely' if punctured.