A word of caution.............
I got a FF3 from Fleet Farm last time they were on sale. The one I got was one of the ones that came with the oversized battery (Chinese made them .7mm too thick). In trying to get the cap threaded in, I stripped it. To Burris' credit.........they sent me another cap in short order. But, had this been for a gun I really NEEDED for this season, I'd have been up a crick.
I'm not sure how you'd know if you got a sight with the proper battery or not. My advice would be to just toss the one that comes with the sight and put a name brand battery in from the get-go.