Great for demonstrating difficult-to-explain resonant waves such as propagation, reflection, and interference. Two cast metal supports, 15.25” tall x 9.5” depth, are extended by connector rods making a frame. A white cotton cloth backing is stretched between the frames to help make the demonstration visible. A 3” diameter spring stretches between the frame ends. Spring steel rods with adjustable weights at each end provide the vibration that influences the wave frequency.