Tung-Sol 6L6GC STR Matched Power Tubes Hard Duet 6L6GC STR Matched Power Tubes Hard Duet Built to the same special tube request specs of leading amp manufacturers of the 1960s, Tungsol 6L6 GC STR Power Tubes are rugged and reliable power tubes that excel in the most demanding guitar amp circuits Choose from soft, medium, or hard in the drop down menu to get the right tube for your needs Soft, medium, and hard style descriptions refer to break up modes of the tube for an overdriven guitar signal Soft tubes have lower plate current and transductance matching numbers and reach saturation and break-up quicker