Want as much gain as possible from your mark I? This is our High gain Option Retube Kit and it contains four 4 JJ ECC83S's, three handpicked High Gain tubes for V1, V2 and V3, an ECC81 for V4 and a balanced ECC83S for V5. The default power tubes are a matched quad of the JJ 6L6GC’s but you can configure this kit to use the JJ 5881’s by clicking on the "Customize" button! If your amp is the combo version and you choose to go with the 6L6GC's then please let us know in the comments section and we will ship your kit with the special Double Mica 6L6GC’s which will greatly reduce any tube rattle.