This Lot of Two U.S.-made Type 27 ST glass tubes was tested on my Hickok 800 for shorts, gas and transconductance. There were no shorts or gas. Transconductance measured: Tube One: 800 micromhos (Zenith stenciled on base w/code R5R M-R Maintenance - Repair; 27 stenciled on glass) Tube Two: 550 micromhos (Ken-Rad engraved on base w/code E7; 27 stenciled on glass) New/nominal is within one standard deviation of 1000 micromhos. I wish I could tell you how they sound, but I do not have a preamp that can run these. Both have bottom D foil getter. This Lot is good for repairmen and DIYers who are working on equipment. I have a number of Type 27s in my store, including matched pairs, please view to see if any fit your equipment needs. Shipping is via U.S. Postal Service Ground Advantage with tracking for domestic sales; Priority Mail is an option for you as well. International sales ship via International Shipping service. Package weighs eight (8) ounces. Combined shipping always welcomed. TUBES ARE GUARANTEED GOOD 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 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: TV-7/U, JACKSON 648 MAXI MATCHER 2.