Due to special unison feed (needle feed & top/bottom roller feed), wrinkle in light material and fine stitch in heavy material. Maintenance-free ball and needle bearing and link take-up lever. Applied full-revolution vertical rotary hook with positive bobbin case opener. Equipped with easy-operating safety clutch which would protect rotating hook from damage. Standard needle gauge: I .6mnn or 2.0mm or 2.4mm. For sewing functional and emmental seams preferably on concave partings of shoe uppers, leather products, etc.