This new old stock-testing matched pair RCA Sylvania Type 56 tubes was tested on Jackson 648 and measured: Tube One: 91% (RCA stenciled on base with code 3-48; bottom D foil dimple getter) Tube Two: 94% (Sylvania stenciled on base with code 339; bottom D foil dimple getter) Good range is between 70 - 130 (70% - 130%) on the Jackson 648 tester. Both are tight on bases with no debris or rattling noise. Nice Type 56 for your needs. I have a number of Type 56s in my store, including matched pairs, please view to see if any fit your equipment needs. View the store for more varieties of tubes for your equipment. Tubes ships via United States Postal Service (USPS) Ground Advantage with tracking for domestic U.S. sale. International orders ship via International Shipping. Package weighs eight (8) ounces. Combined shipping always welcomed. TRANSIT VIA POST CAN DAMAGE TUBES. THIS IS NO FAULT OF OURS BUT THE THIRD PARTY ENTITY THAT IS DELIVERING ITEM(S) TO YOU, I.E, USPS, UPS, FEDEX, YOUR NATIONAL CARRIER IF INTERNATIONAL, ETC. PLEASE INSURE THEM! WE CANNOT GUARANTEE FAILURES ON YOUR EQUIPMENT AFTER POWER UP AS THERE IS NO WAY TO ASCERTAIN HOW TUBES WILL INTERACT WITH YOUR ELECTRONICS; NOR IS THERE A WAY TO DETERMINE WHETHER THEY MAY HAVE FATAL FLAWS IN TUBES THEMSELVES! THESE ARE USED VACUUM TUBES AND TIME MAY HAVE TAKEN A TOLL ON THEM OVER THE MANY YEARS SINCE THEY WERE MANUFACTURED. WE CAN ONLY TEST FOR THE PARAMETERS MENTIONED ABOVE IN ONE OR MORE OF THE FOLLOWING EQUIPMENT WE USE FOR MEASURING: JACKSON 648, TV-7/U MAXI MATCHER 2.