Rayon String Wound Filter Cartridges have a fluid compatibility similar to bleached cotton, but are more coarse and less absorbent than cotton. Swells in aqueous solutions. They are spun wound to micron ratings from .5 to 200 and are manufactured in our facility in Coleman, Texas. For use to 300ºF. String wound filters are a 'depth' filter created by winding diamonds onto a core with 1" to 4" of filtration media. Depth Rayon filters provide a high dirt holding/retention capability with low media migration.