Four 5R4GYB Vacuum Tube - Hickok Tested - Lot #5: These tubes tested very strong on our Hickok 534 Mutual Conductance Tube Tester. We have been successfully selling vacuum tubes here on Ebay for over 17 years & so far have not had any problems. Please bid with confidence. We do not give out our tester readings due to the fact that no two testers will test exactly alike & we avoid any problems by not divulging our readings. All of our tubes are guaranteed to be as seen & described.