The Electro-Harmonix 6L6EH Power Tube is modeled after the vintage RCA 6L6GC "blackplate." Features large plate dimensions and improved grid structure for increased power handling capabilities. Also features mica spacers with metal springs to eliminate tube rattle and microphonics. The 6L6EH offers tone and performance superior to any other 6L6 or KT66 type. These are Electro-Harmonix 6L6EHs in platinum matched sets. Their platinum matching process consists of a 24-hour tube burn-in period followed by a bias (plate) current measurement in milliamps.