Coalescing (Pre-Filter) Filters Often called the pre-filter since itis placed on the air line just prior to the air dryer, a coalescingfilter removes oil, particles and moisture before it can come incontact with the desiccant in the dryer and ruin it. Our Coalescing Filter Replacementscome with a manufacture's warranty that matches or exceeds theoriginal OEM warranty. Original equipmentmanufacturer (OEM) names are the trademarks of each manufacturer.On products marked "replacement," OEM names and part numbers arefor reference only.