TUBES ARE GUARANTEEDGOOD AND IN WORKING ORDER AT SHIPMENT. 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 POWERUP AS THERE IS NO WAY TO ASCERTAIN HOW TUBES WILL INTERACT WITH YOURELECTRONICS; NOR IS THERE A WAY TO DETERMINE WHETHER THEY MAY HAVE FATAL FLAWSIN TUBES THEMSELVES!  THESE ARE USED VACUUM TUBES AND TIME MAY HAVE TAKENA TOLL ON THEM OVER THE MANY YEARS SINCE THEY WERE MANUFACTURED. WE CAN ONLYTEST FOR THE PARAMETERS MENTIONED ABOVE IN ONE OR MORE OF THE FOLLOWINGEQUIPMENT WE USE FOR MEASURING:  HICKOK 600A, HICKOK 800, MAXI MATCHER& MAXI MATCHER 2.