Two sixes nose to tail( 12v combined, wired just like batt.s in a
flashlight), gives you more run time. The 12v gives you a couple of options
when it comes to terminal connections: Some folks like the standard top-post,
others want top and side posts. Optima makes both flavors in the 12v Yellow
top Deep Cycle. It all depends on where you want to mount the batt. And BTW,
the 65amp/hr rating of these batt.s is an understatement to say the least.
Hope that helped,
Beckett