A pair of original - made in Czechoslovakia - Tesla EL34 tubes with the Zavod Trinec Factory Code 37. One is cobalt blue glass, labeled Tesla, and the other is labeled Penta Labs. Construction is identical. They were sold to me by an Audiogon dealer as new but I don't have a tester and can't verify whether they are matched. I've put them into my Cary Sli-80 amp and they work perfectly with beautiful sound and steady bias. If they don't work for you I'll refund your money
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