Final answer:
The 300 series of stainless steel is used to manufacture malleable retractors due to its excellent corrosion resistance, high toughness, and ductility.
Step-by-step explanation:
The series of stainless steel that is used to manufacture malleable retractors is the 300 series. This series is also known as the austenitic stainless steel series. It is characterized by its excellent corrosion resistance, high toughness, and ductility, which makes it ideal for medical instruments such as retractors.