While the NIJ performance standard is used by many countries, Germany has its own rules for testing body armor. Though similar to the American safety standards, Germany’s testing goes beyond NIJ in some performance characteristics.
The German SK1 standard is quite different from the American NIJ certification. While both the German and American standards use 9mm test rounds, the type of bullets used are very different. The 9mm ammunition used for SK1 testing are Action 4, QD-PEP and DM41 SR expanding rounds.
The SK standard also includes 0 meter distance contact shots which are not part of the the NIJ standard, though FBI body armor test protocols also include contact shots.
The German SK1 and FBI protocols also include extremes of heat and cold. Armor samples are hit-tested at 70 °C (158 °F) and -20 °C (-4 °F). Manufacturers of flexible ballistic packages that have been certified according to SK1 must warranty their panels for 10 years, while the usual warranty for NIJ certified panels is 5 years. Body armor with NIJ Level II protection according to the latest NIJ standard is roughly equivalent to the German Schutzklasse 1 protection level but there are some notable differences.
Table Ballistic Resistance