Mess-free! Steel filings are safely sealed in a scratch-resistant, transparent viewing tray for your investigations. Each kit includes rubber-coated magnets (0.75" disc magnet and 1" bar magnet) and filing-filled tray measuring 3.44".Details:Clear viewing of the invisible lines of a magnetic fieldSet of 3 kitsEach kit includes 2 magnets (0.75" disc magnet and 1" bar magnet) and filing-filled traySteel filings are sealed in a scratch-resistant, transparent viewing trayMagnets are rubber coated to prevent scratching on the outside of the trayFor ages 8 and up