Contains a pair of suction cups with handles (also known as Magdeburg Hemisphere), Finger hole diameter is 1 inch. When one suction cup is stuck to a flat smooth surface it can take up to 26lbs of force to separate it from the surface (with maximum adhesion) Diameter of suction cup is 3.25 inches (slightly compressed), each half is 2 inches tall Great for fixing dents, holding a surface, or doing a science education vacuum experiment When suctioned together a minimum of 100 newtons (22lbs) is required to separate them Pair of Industrial Suction Cups (3.25 inch dia.) with handles and release stubs, also known as Magdeburg Hemisphere, 100 newton (22lbs) separation force. Demonstrates the force of air pressure without a vacuum pump. In this modern variant of a famous 17th-century experiment, student place the edges of two hemisphere cups together and squeeze them, forcing out the air between them. In a tug of war, students try to pull the cups apart, surprisingly difficult task. Each of the 7.5 cm diameter rubber hemisphere has a 2-finger tug handle and 2 release posts.