(!!!!) (Best Pair) 5R4GB GE black base NOS 1981 (50-52/40 and 50-53/40 x 2 tubes)
By Tube World
$ 39.99
1 pair) 5R4GB GE black base NOS 1981 (MS)
1 tube) 50/40 and 53/40
1 tube) 50/40 and 52/40
5R4GB black base = 5R4GYB with brown base
See more: vacuum tube
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 (Best Pair) 5R4GB GE black base NOS 1981 (50-52/40 and 50-53/40 x 2 tubes)&Category=vacuum tube&ImageURL=http://tubeworldexpress.com/cdn/shop/files/1_738cf4e4-2fac-4a4f-90d2-334b18f8ff96.jpg?v=1684847587){kind=link}
 (Best Pair) 5R4GB GE black base NOS 1981 (50-52/40 and 50-53/40 x 2 tubes) "Pin It")