Why are almost all production plastic injection molding core and cavity inserts made from steel? Steel is certainly NOT the hardest material. Steel is also definitely NOT the most corrosion resistant material. Finally, steel most assuredly is NOT the best conductor of heat. So why are production tools made from steel? The real answer is probably because that’s the way they have been made for many years. People are used to working with steel molds. The results are predictable. However, as two mold case studies, in addition to Finite Element Analysis (FEA) results presented in this paper will show, there are now commercially available inserts that achieve: (1) shorter lead times, (2) faster cycle times, (3) enhanced productivity, (4) lower unit part cost, and (5) reduced part distortion.