DYNACO  REPLACEMENT OUTPUT TRANSISTOR SET. THESE  OUTPUT TRANSISTORS FIT THE ST-400/410/416 SERIES AND ST-150 POWER AMP AS WELL AS MANY OTHER BI-POLAR POWER AMPLIFIERS. THE ORIGINAL DYNACO OUTPUT TRANSISTORS WERE RATED AT 120 VOLTS 16AMPS 200WATTS. THESE DIRECT REPLACEMENT ON SEMICONDUCTOR DEVICES ARE RATED AT 250 VOLTS 16AMPS 250WATTS.  (According to ON, they have the largest die of any TO-3 power transistor on the market which means they can dissipate more heat and operate more reliably.  YOU WILL RECEIVE (1) #571104 (2N5630 REPLACEMENT ) AND (1) # 561356 (2N6030 REPLACEMENT) OUTPUT TRANSISTOR. MATCHED SET. TOPS WILL BE MARKED FOR EASY IDENTIFICATION. BLACK  FOR #571104 AND RED  FOR #561356. FULLY TESTED . THANKS FOR LOOKING.