Want all the gain you can get? This is our High Gain Option Retube Kit for the Bogner Metropolis Heads and Combo Amps. It contains a matched quad of JJ EL84's for power, a JJ GZ34 rectifier tube, a single EL84 for the reverb driver, two standard ECC83S's for V10 and V11 along with three handpicked High Gain ECC83S's one being current balanced for the phase inverter in V3. Just let us know in the comments section if you're looking for an early breakup, a moderate breakup or a later breakup for more headroom in which case we will choose the coolest grades we have available for the power tubes.