Here we have matched quad set of superb Svetlana 6L6 GC Replacement Valves / Tubes. These 6L6 Svetlana tubes / valves are among the dozens of spare valves that I've accumulated over the years as spares and backups for various Mesa Boogie amps and pedals I've owned. Apart from being matched and 10-15 hours use in my amp they've hardly scratched the surface of their long life.