The Harbottle Pressure Globe helps students to understand the meaning of fluid pressure and pressure reduction. Simply place a balloon into the opening of the glass Harbottle and stretch the mouth of the balloon over the opening of the bottle. Blow into the balloon and, when it is fully inflated, stopper the bottom hole of the Harbottle. The balloon will stay inflated even though it is open to the atmosphere. This apparatus is an excellent tool for teaching pressure, vacuums, and weather. Includes Harbottle, balloon, rubber stopper, and instructions included.