Shimpo FG-M6FTG20U Grip Adapter Flat Chuck Tensil Grip). Shimpo Flat Chuck Tensile Grip 100 lb Capacity, Accepts Samples to 20mm Thick, M6 Thread. Each serrated gripping face is 0.79" (20 mm) square and can accept samples up to 0.79" (20 mm) thick. Shimpo parts and accessories