WIX HD Air Filters feature premium filtration media with skip a pleat media stabilization (where applicable) and pleat stabilization beads. WIX HD Air filters are recommended for OEM air filter change intervals. Polyurethane and or high strength corrosion resistant end caps and expanded metal bodies ensure a durable long lasting filter. Air filter Laboratory Tests per ISO 5011: Minimum efficiency of 99.9% contaminant removal. (Based on Wix 46664, Wix 42803, Wix 46761, Wix 46433 )