All the plugs that are posted here are exactly the same heat range, so you have a couple of choices to make 5/8" or 13/16", standard or extended tip, and what brand you like. As I posted AR3933 is 5/8" standard tip and AR3910 are the same heat range but with an extended tip. I have ran them both and both work fine, the AR51 has a 13/16" socket size and the AR3933 and AR3910 use a 5/8" socket I like the 5/8" because it's smaller and sometimes you might need a little more room around the headers