This Pencil style tension gauge is used to set proper top thread tensions. The Top Thread Pencil Tension Gauge has a hook with a sliding guide on one side for setting top thread tension on commercial embroidery machines. The sliding needle works in conjunction with a spring to indicate whether you need to tighten or loosen the top thread tension. To check your top thread tension, have your embroidery thread correctly threaded through your machine’s running path including through the needle and presser foot. Wrap the end of the embroidery thread around the hook end on the gauge so that it catches without slipping. Slowly and steadily pull the gauge back toward yourself. Note the common number seen on the gauge’s needle. Top thread tensions may vary up or down by as much as 5 to10gf. Rayon #40: 150gf; Polyneon #40: 170gf; Metallic #40-50: 170gf; Polyester CR #40: 125gf; Burmilana #12: 190gf. Comes with instruction manual. YICBOR Thread Tension Gauge Compatible with TAJIMA Brand SWF Brand Ricoma Brand Commercial Embroidery Machines.