A white frame with transparent window containing magnetic powder in a water based solution for showing magnetic field patterns. When a magnet is present the particles of iron inside become slightly magnetised so they attract each other and cluster into the lines that show the magnetic field patterns. This can be used for showing magnetic field patterns either on the bench or on a overhead projector. Alternatively the device may be placed over a piece of white paper to provide background. It may be used to show fields in much the same way as with loose iron filings on card but with much greater convenience. Supplied with two pairs of bar magnets and an instruction/experiment booklet.Dimensions: 225 x 130 x 15mm. WARNING! Not Suitable for Children under 3 years due to small parts.This product contains magnets or magnetic components.Magnets can cause serious or fatal injury if swallowed.