On Sat, 17 Mar 2012 19:54:22 -0700 (PDT), DerbyDad03
wrote:

So is the different number of drivers on the different 16" chains
based on the gear that drives the chain? In other words, why does a
16" chain for one Stihl model have 56 drivers, another 16" chain for a
different Stihl model have 57 drivers, etc?

The drivers affect the match to the gear. Same as if you were matching
teeth on two gears. If one gear has 10 teeth per inch, the other one
needs the same or they wont mesh. The amount of teeth dont matter, it's
the drivers must match the gear or it wont work. Then the bar needs the
proper thickness of the drivers to fit correctly in the groove.

Look up the make and model of your saw on the web. Find a downloadable
manual, it will tell you what to buy, or give you a phone number to
call. The packages on those generic chains are mostly worthless.