The E88CC are the "Select" version of the ECC88 6DJ8/6922. Vintage Mullard and Telefunken E88CC were usually made with GOLD PINS and have very close triode balances and very low noise and are typically longer lasting. I currently own sets of 4 Telefunken and 4 Mullard E88CC. I am in the process of evaluating both sets of tubes in my ARC LS25 MKI. I am also experimenting with vintage Mullard and Telefunken ECC88. Incidentally, the set of 4 Telefunkens (E88CC) was quite expensive (approximately $350 used). NOS of these tubes can run up to $600). Even with the regular vintage Mullard and Telefunken ECC88, the ARC LS25 MKI soars and goes up several notches in performance.