Defender Full Mask project is an innovation initiated by Undip researchers Wahyu Caesarendra, ST., M.Eng., Ph.D. from Mechanical Engineering who is currently undergoing Visiting Assistant Professor in Universiti Brunei Darussalam, dr. Satrio Adi Wicaksono, Sp.An., from Faculty of Medicine and Tri Ratna Darma Putra, ST. is Undip alumni who founded a company in the field of industrial machinery and laboratories equipment. This project is conducted to help the medical forces in the hospital who need full protection mask while nursing people with COVID-19. As per the description video uploaded to YouTube on April 26, 2020 entitled: “Defender Full Mask Project (alternative APD in Indonesia)”, The “Caesar valve” adapter is designed to have features and working principles that adjust the design and the working principle of a full face snorkel mask is to have a 2-way air flow system. With the 2-way airway system, if we breathe, the air in the full-face snorkel mask is not easy to get foggy. The air in a full-face snorkel mask is comfortable to use. So that this mask can be used in longer period. Another advantage of the engineering side is that the “Caesar valve” adapter utilizes a 1-way valve system (similar to the working principle of the check valve) which is designed at one end of the pipe, namely at the end of the respiratory exhaust pipe (CO2). This is intended so that air that has not been filtered cannot enter the filter and can only enter from the pipeline that has a filter installed. At present the “Caesar valve” adapter has been produced on a limited scale in Semarang, Indonesia. “Caesar valve” adapters are made from Poly Lactid Acid (PLA) polymeric materials and flex. Flex is a softer type of material and PLA is a hard material. “Caesar valve” adapters are manufactured with 3D printer machines and are designed using SolidWorks software by Dr. Wahyu.