Quote Originally Posted by driver3
this is the link I meant
http://www.1st-optima-batteries.com/faq18.asp
The blue and yellow top are the same, except blue has extra terminals

From the link
"The D31-series batteries are the largest made by Optima. The only differences are in the type of electrical connections and the color. There is no difference in the internal construction or performance of these three batteries; they are electrically identical. "
Except for the difference in the CCA's. The D31 is 900 CCA's. shawn