I installed a quad of these in my Ampeg V4B last week. The matching from The Tube Store was perfect! Each tube is within 0.5 watts of the others at idle. These are really high quality tubes BTW. They did run a bit cold, so I had to tweak the bias a bit to get them up to where I like to run them. At 50% of their rating (about 17 watts), the amp is VERY clean, making over 100 watts with ease, and no signs of cross-over distortion. They should last forever running this way. These are very heavy-duty tubes, with extra heat radiating fins added to the plates, very thick glass, and good metal suspension of the element. You really can't do better for a current production 6L6 variety tube, but you will likely need to adjust the bias. I'll be getting more to re-tube some of my other amps.