SPECIAL THREAD, METRIC SIZE, CARBON STEEL, HEX DIE. CARBON STEEL HEX DIES ARE FOR DRESSING OVER BRUISED OR RUSTY THREADS, THEY ARE THE MOST COST EFFECTIVE RE-THREADING TOOL AVAILABLE. NO SPECIAL HOLDER IS REQUIRED FOR THIS TYPE OF DIE, ANY WRENCH LARGE ENOUGH WILL SUFFICE. IDEAL FOR MAINTENENCE IN THE SHOP AND FIELD.