Compression set or Compression resistance
For foam products in shoe manufacture we like to know how long foam will last if we build it into a footbed or shoe midsole. Simply put the compression set is how much a foam will bounce back after being compressed. Compression set is measured in a Percentage. A foam that resists compression could have a score of 4%, a foam that is badly damaged by impact may have a score of 45%.
Poor quality EVA will have a high compression set value. High quality PU foam will last forever with a very low compression set. Injection Molded EVA like this shoe will resist compression set.