(!!!!) (Best Pair) 5R4GB GE black base NOS 1981 (51-54/40 and 52-55/40 x 2 tubes)
$ 39.99
1 pair) 5R4GB GE black base NOS 1981
1 tube) 51/40 and 54/40 (NS)
1 tube) 52/40 and 55/40 (JS)
5R4GB black base = 5R4GYB with brown base
See more: vacuum tube