Racing Rings consists of three rods one each of copper, aluminum and PVC, Ring magnet is dropped down the PVC rod, it falls unobstructed, Two metal rods create an induced magnetic field to that adds resistance to the rings travel, metals are different, they fall at different rates
Resonance Tube Apparatus, Long version, Material: Acrylic, Mounted on retort stand with clamp and boss, with metal vessel, connecting tubing and spring clip supported on iron ring, Dimension: 120cm