pith ball Brand: WKM Features: Pith electroscope for demonstrating static electricity Two pith balls suspended on unspun silk string to test for charged objects Plated brass pillar for durability Plastic base for display Suitable for high school or college students, or ages 14 to 21 Binding: Electronics Part Number: BSP255 Package Dimensions: 2.0 x 1.2 x 1.2 inches