Sprung wagon W-irons using piano wire as the spring. Designed for any 4mm scale wagon irrespective of the mass of the wagon; the only adjustment required is the selection of the most suitable wire material and or diameter (0.011″ supplied) to give the required ride height. Best used with waisted bearings. Full instructions included. Sufficient for three 4-wheeled wagons, such as 12T vans, 16T minerals and 13T opens.