I am using the .22 uf CuTF as coupling caps in my BAT 150SE amps. They replaced the TFTF caps which themselves were a big improvement over the stock caps. Now in comparison, the TFTF caps seem more clinical compared to the CuTF caps. The highs are smoother, the midrange fuller and more lush, and the overall sound is more involving and musical. The best of a copper PIO combined with the best of teflon.