:"12? Or are they saying that both ends of the connector will accept either 10 or 12?"
Option 2. and that's the one you want... In some cases you might wish to consider a split bolt (those hold much stronger but are much larger as well).
I have a commercial grade crimper (Way too expensive) does a fantastic job of crimping the leads.. It is designed for Anderson Power poles but if you take the plastic stop off it's a general purpose ratching crimper.
NOTE Crimp on's do not work well on SOLID Wire.. Solder does (or crimp on then solder)
