This is a suitable replacement for any EL34 = 6CA7 POWER PENTODE tube type. Various brands available.
These Tesla E34L (Special Quality EL34) are NOS with black bases in original Tesla boxes, and are one of the best NOS EL34 values around. Perfect for that old Marshall! Special price of just $119.99 per tube! Matched pair enter qty 2, matched quad enter qty 4. $5 per tube for matching! Get 'em while they last! Tesla black based is considered by alot of guitar players as hardier tube than the brown base version, and the black base could take more plate volts and thus really growled when at high volumes. High volume distortion was more like the Mullard EL34---in Marshall amps.