Zipper Slider & Puller Torsion Tester. This unit can perform a test to determine the torsion strength of Zipper slider & puller. By holding the puller and slider in separate jaws of grip in this unit, and twist them to measure torsion strength until the connection of slider and puller breaks; or a rupture of some other kind occurs. It is useful for metallic, plastic, nylon zipper. https://fyitester.com/for-sale/zipper-slider-and-puller-torsion-tester-fy-iv/