... duty lockstitch sewing machine, GB4-1 model is used to sew canvas, container bags, belts, leather, tent, ... heavy duty lockstitch sewing machine, GB4-1 model is used to sew canvas, container bags, belts, leather, tent, ... Oversize oscillating shuttle may be used to increase thread volume and to reduce number of times of thread ... stroke: 58mmShuttle hook: SEIKO HSH-7-3 PP woven bag sewing machine GB4-1