the unmatched manufacturing process makes these polypropylene (pp) bags the very best in quality.   features:   ·         thermally sealed at edges to stop fraying of fabric ·         100% pp bags, even stitching is done with pp thread ·         the strings (duses) are also made of the similar pp woven fabric unlike competitors. all these features provide consistent filtration with very long life. This makes our bags the most economical and efficient.