Insulated runner tools resemble more traditional cold runner molds but utilize cartridge heaters or other methods of heating to form a surrounding layer of molten resin, forming an insulated "cull" to create a similar effect to a hot runner system. This approach is less expensive than using a hot runner which requires a temperature controller and also has the benefit of allowing for faster color and material changes. However insulated runners are not suitable for all types of materials and typically do not work well with more demanding engineering grade resins.