OK where do I start. There is a ton of mis leading information about adjustable Vacuum advances out there. None of the mopar NOS or aftermarket are adjutable for the amount of advance, just the rate of advanc. Yes you can limit them with wire etc, but they are just adjustable by the rate of advance. That is by vacuum. The ones that are adjustable have the hex on the end of the vacuum advance like the one on the right in the picture. You use a 3/32 allen wrencd and turn it clockwise to lower the amount of vacuum needed to start the advance and CCW to increase it. The cutaway shows it. Also, there are two different arms one is straight, and one is curved on all platforms 6/LA/B/RB make sure you order the right one, depends on the advance plate. NOS is great but do not be surprised if it does not hold vacuum, they are 50 years old and have a rubber diaphram in them that can be in poor condition. Hope this helps out.