These were factory in an amplifier I bought second hand. The previous owner had played it into the ground... V1 was still good at 5 years old, the PI tube too. V2 was a bit hissy but I would suggest that for the price they lasted extremely well. I purchased the 12ax7a as a replacement and side by side I cannot pick a difference, honestly. Perhaps they are the same tube and the Bs are just selected for higher measurements. Anyway, they are punchy and loud. In v1 they are whisper quiet although in a chain a bit noiser than more expensive valves. The structures in the tube are a bit lopsided, one rattled out of the box and also the pins are quite soft, but they are so cheap and sound pleasant.