These are the five most common tig torches.  Most manufacturers use these numbers and most  parts are interchangeable between them.   The #9 is a 125 amp air cooled torch.  The #17 is a 150 amp air cooled torch.   The #26 is a 200 amp air cooled torch.  The #20 is a 250 amp water cooled torch and the #18 is a 350 amp water cooled torch.  If you need information on any other torch contact us and we will get it for you.