FOR SALE IS A NOS NIB QUAD OF TUNG SOL DYNACO BRANDED 6550 KT88 VACUUM TUBES. See pictures of actual tubes and test results. Two date code matching pairs that are perfect for a push pull stereo amplifier or a pair of mono blocks. Crystal clear glass. Gleaming chrome. No shorts, no gas, no leakage. They test and appear to be new old stock but should be considered used and as is due to thier age. On my tv7d/u they test 80, 80, 80, 82 out of 44 min.