SX series is a 3 needle feed off the arm, double chain stitch machine with upper puller.
Applications: lap seaming or side seaming on heavy weight fabrics such as jeans and work pants.
Major features of this series are upper puller and differential feed mechanism.
These features feed the fabric uniformly so that the machine can inseam jeans even at the cross seam sections.
Puckering is no longer your concern.