DescriptionFrom Mesa Boogie:The MESA® 5Y3 RECTIFIER TUBE is a favorite among vintage aficionados and a great choice in older MESA amps like the Lone Star Special as well as many other vintage, non-MESA, amplifiers. This tube produces sultry, vintage sag, creating a silky-smooth feel on the strings that is incredibly addictive to play. It provides the most sag of all of our rectifier tubes.