These adapters will allow you to use a 6BG6GA to replace a 6L6,6L6GA,6L6GB,6L6WGB or 5881. MOST 6BG6GA CAN NOT BE USED TO REPLACE A 6L6GC,7581A or 7027A. If your amp uses a 6L6GC,7581A or7027A you can use a Philips/ECG 6BG6GA . These tubes have a higher wattage plate and will stand up in 6L6GC,7581A,7027A applications. DO NOT use any other brand 6BG6GA in 6L6GC,7581A,7027A applications they will not hold up and you could damage your amp. Any 6BG6GA will work for 6L6,6L6G,6L6GB,5881 applications. You can do a google search . Many have tried these will excellent results.T are Black Plate versions of the 6BG6GA.A 6BG6GA is a mechanical redesign of a 6l6.Below is a quote from a Tung-sol 6BG6 data sheet. “The 6BG6G is essentially a mechanical redesign of type 6L6G to permit operation as a horizontal deflection amplifier for television service .It uses a top cap connection and additional insulation for the plate structure to withstand the high peak voltage encountered is such circuits”. -The only difference between a 6BG6GA and a 6BG6G is the glass envelope. If your not happy with the $50 plus price for NOS 6l6's, 6BG6's go for somew between $6-$10 each. Still affordable to lay in life time supply. You will need extra room to accommodate the extra length of the adapter. The total length of the adapter and tube is 6 inches. PLEASE NOTE:This is the first batch of adapters I made . The adapter will only work for 6BG6GA tubes. It will not work for 6BG6G tubes. The 6BG6G is a little taller . I didn't make the top cap wire quite long enough for these tubes. It works fine for the 6BG6GA.