This set of 6 drilled balls provides a multi-material collection for pendulum experiments and comparative physics investigations. Each ball measures 25mm in diameter with a 3mm drilled hole for threading on a string, wire, or rod. The set includes one ball each of wood, aluminum, steel, copper, brass, and lead. The variety of materials with different densities allows students to investigate whether mass affects pendulum period, compare gravitational acceleration across materials, and explore concepts of density and inertia. Suitable for physics experiments involving pendulums, projectile motion, collision dynamics, and density measurement.