Help Please - What are the correct lengths of plunger rods

[swinks]

What is the correct length of a plunger rod from the shoulder of the know that that you grab where the spring rests to the tip where the rubber tip slides on for a:

Bally / WMS 90's game - mm / inches
Stern 2000's game- mm / inches

I have older games, never NIB so I don't know what is the standard, so any help would be much appreciated. I want to work on a custom rod but don't want to stuff up. Or are all shooter rods the same length as I found this
http://www.pinballlife.com/index.php?p=product&id=1608

I am guessing this is a Bally almost 7  7/8inches, my IM came with a custom rod so can't compare with anything

[Boots]

Not all shooters are the same length, but I am not sure what the lengths are exactly
I think all Williams are the same, I am pretty sure the older Gottliebs are a bit longer

[Richyrich]

7  7/8"  sounds right for B/W

[dendoc]

And who's the sadistic bastard that added the spike to the end of the plunger? surley hitting it didn't damage too many machines in the old days?