I own a few nice protractors including the DB Systems and a custom mirror one, but since I started branching out into a wider range of arm lengths and types I've taken to using the
Chpratz protractor I downloaded off Vinyl Engine and calculating my own null point pairs using the calculator on the site. I did have to carefully resize the download to get the measurements to be precise, but it wasn't difficult. The DB Systems was great for my 9" arms, but I run a couple in the 10" and 12" range now and the standard options really weren't cutting it. Even the null points from the manufacturers lit didn't work out as well as what I worked out so to say I'm happy with the system would be an understatement.