... ", 4", 5" 3. Thread: M14x2 ,5/8" -11NC Flexible Back Up Holder Flexible Back Up Holder are used for grinding profiles or curves surface ... ). Made from rubber, they flex in the direction of the pad. Great for edge and flat surface grinding and polishing. Model ... ,5/8" -11NC 003125mm(5")M14x2 ,5/8" -11NC Flexible Back Up Holder