Precision Filters 1) Grades: HF9, HF7, HF5, HF3, HF1 five grades 2 ... closed cell foam sleeve 4, Ultra high efficiency oil removal filter (HF3)For coalescing ultra-fine oil aerosols; removes solid ... stage—coated, closed cell foam sleeve acts as pre-filter and flow disperser Second stage—multiple layers of matrix blended ... migrationDesigned for 1000 hour life at rated conditions. Precision Filters