In order to produce sound inclusion free castings of good quality it has been extensively proven that filtration in the mould is of prime importance. Dross stringers,especially magnesium-sulphides,oxides and silicates are the main sources of non-metallic inclusions and a big problem for all ductile iron casters.They can impair mechanical performance and lead to an unacceptable cast surface.It is therefore,of primary importance to reduce,or better,prevent inclusion related defects,which result in unacceptable castings either before or after machining.Efficient removal of slag,dross and other non-metallic inclusions can be achieved by the use of a ceramic foam filter,along with a correctly designed runner system.