Two needles and 3 or 4 thread capabilities. Tackle heavy fabrics: Serge with confidence on multiple layers of denim, layered knits and heavy duty fabrics. Professionally cut and finish in one easy step. The Strong & Tough high durability blade is manufactured of carbon steel that can cut a smooth, clean edge even through heavy fabrics.Heavy duty metal frame: Helps ensure your serger remains stable on your work surface, even at very high speeds; built for durability and longevity, for many years of extended use.