SWMFG stands for Southwest Machine & Forge. No Cat indicates that these spring plungers do not have a cathodic protection coating. Spring plungers are devices used to exert force on components. Typically made of steel or stainless steel, they feature a compressed spring that is activated when the plunger is inserted into a hole. SWMFG No Cat Spring Plungers are crafted from high-quality materials, ensuring durability and longevity.