darrell reponse is correct i agree with him. i use a sencore mu complete tester.in all reality if you are gonna buy tubes esp nos you must have your tester,and one that tests mutual conductance.i test tubes for my friends and match them.you need to find someone in your area who will do that.there are alot of people who sell tubes and have no questions ask return policy.the best tester ive had is the sencores,i know others prefer hickoks but not me i prefer sencores.you can usually pick up the the sencore mu150s for 300 to 500 dollars,they are great testers in my opinion.i have 2 of them.they are not for sale.good luck.
