The Coupling is a replacement part for the K3/K5 torch. You can identify where this part is used by cross reference to the parts manual below. Our most popular and widely sold design torches. The K3 is a general-purpose 600amp carbon arc torch for use with 3.2 to 9.5mm gouging carbons. The K5 is a 1200amp torch for use with 4.0mm to 15.9mm carbons.