Demonstrates that objects fall at the same rate of acceleration in a vacuum despite their relative weights and sizes. Consists of a durable glass tube (81 x 3.5 cm) equipped with end caps, one of which has a hose cock for evacuating the tube. Includes instructions. Vacuum Pump with Gauge (item #752836 or #752836B) and Vacuum Tubing (item #711558) are needed but not included.