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
Test tube drying racks, plastic, 50 place rack features a 5 x 10 array of pegs that hold tubes up to 16mm in diameter, polypropylene, conveniently hold inverted tubes for drying and to minimize collection of airborne contaminants