The Mesa/Boogie 5AR4 rectifier tube produces a vintage feel with light to mild "sag." While it produces more "sag" than silicon diodes, it is the least "saggy" of the Mesa/Boogie tube rectifiers. Used in vintage Mesa amps like the Heartbreaker, Blue Angel and Maverick as well as many other vintage, non-Mesa amplifiers, Mesa/Boogie rectifier tubes are premium grade and offer unsurpassed consistency and reliability.