Actually this AL-1200 from HRO came with the 3CX1200Z7, although the add indicated it was the 3CX1200A7 and the receipt had same info. The tube went into the socket fine so the amp was designed for the Z7. No complaints -- I understands it a more rugged tube First time using a 220V amp. Big improvement over a 115 volt amp. Runs SMOOTH. Eric VY1EI