The IEC Potentiometer (slide wire type) is a classic instrument for teaching electrics. We have both 1m long EM2450-001 and 1/2m long EM2451-001 high quality models. The 1m model has 2m of wire length and the 1/2m model has 1m of wire length. Construction is similar for both models, with aluminium channel base (to avoid the warping and cracking of wood) and a metric rule lies below the 2x lengths of 'Advance' wire (that does not change resistance with temperature). A 'Jockey' is provided for making accurate contact with the wire and the exact position of contact is read on the rule in mm.