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These are extension dampers. They are not shocks. These extension dampers control the extension stroke opening speed based on the "N" or Pound rating of the unit. It operates based on gravity, so these are perfect for drop down applications that you want to control how fast it lowers. The range for any specific N value on dampers can be +/- 2.5N from 5N to 40N and +/- 5N for 50N and up