Safety filters have two functions: to act as a backup to the primary filter and to protect the engine during primary filter servicing. Serve as a backup filter in case of primary filter damage or improper installation. Prevent contaminants from entering the clean side of the air intake system during primary filter servicing. Designed to plug rapidly if contamination finds its way past the primary filter, alerting operators about an issue. Recommend that safety filters are replaced with every third primary filter change unless there has been a failure of the primary filter. Specifications: Outer Diameter 211.5 mm (8.33 inch) Inner Diameter 155.5 mm (6.12 inch) Length 297.7 mm (11.72 inch) Efficiency Test Std ISO 5011 Primary Application CATERPILLAR 6I2508 Type Safety Style Radialseal Brand RadialSeal Media Type Safety