Magnetic Field Viewer
Visualize a magnetic field easily and clearly without mess or safety concerns. With this special viewer, iron filings are safely sealed in a 3.25"-diameter flat plastic tray. Just tilt the tray back and forth to spread the iron filings and then move a magnet under the bottom of the tray to see the magnetic field "map" itself. The viewer comes a ceramic disc magnet that's 1-1/8" in diameter and also a ceramic bar magnet that's 1-1/4" long.