guru-butyu-bu is a reliable vacuum tubes to the 3rd brands are favored by top musicians in the world for over 30 years. The Mark of the world, part of selected only from the vacuum tube in the GT obtained from and sold. Stable and reliable sound and the quality. Matching power tubes are in the alpine 2 piece set, 4 piece set, PRI has 12AX7 and 12AT7 tube combined with chess set, also available.