Metal - Our "metal" amp tube kit is designed to produce richer, thicker, and darker tones. This amp is built around EL34's and includes a "high gain" preamp tone kit, and 2 x Electro Harmonix 5U4GB's. The Ruby EL34BSTR will give you a "wall of sound" and the attack and response needed in metal. Electro-Harmonix 5U4GB's are one of our best, most sturdiest rectifiers. Our preamp tone kit is all high gain, designed so you can push your amp and is as followed: V1 - Mullard CV4004 (High Gain) V2 - JJ ECC83 (High Gain) V3 - Shuguang 12AX7B(High Gain) V4 - Shuguang 12AX7B(High Gain) V5 - Mullard 12AX7 (High Gain) Rock / Hard Rock - Our "rock" amp tube kit is designed to produce richer, smooth, fuller bodied tones. We recommend the Tung-Sol 12AX7 in V1 - it will give the clean channel a three dimensional sound. Our preamp tone kit will give you the flexability needed in rock, and is as follows: V1 - Mullard CV4004 V2 - JJ ECC83 V3 - Shuguang 12AX7B V4 - Shuguang 12AX7B V5 - Mullard 12AX7 reissue