Coleman Filter Company Polyester String Wound Filter Cartridges have a chemical resistance similar to polypropylene, with higher temperature resistance. They are spun wound to micron ratings from .5 to 200 and are manufactured in our facility in Coleman, Texas. For use to 350ºF. String wound filters are a 'depth' filter created by winding diamonds onto a core with 1" to 4" of filtration media. Depth Polyester filters provide a high dirt holding/retention capability with low media migration.