$500.00 plus $12.00 shipping Maybe trade for a quad or pair of Mullard EL34 xf2 Blackburn tubes. 70's vintage KT88 pair! Identical dates codes and nearly identical output! Triple Getters Output tested at 100 and 102 Life test at 105 and 105 Date code 7042 Z Tubes were tested on B&K 747B. All proper testing procedures were observed. Tested for shorts and grid emissions. Tubes will be shipped fully insured for purchase price and will require a signature. As tubes can be damaged by improper handling or faulty equipment no returns will be accepted after delivery, so make sure your using the proper equipment equipped for these wonderful rare tubes.