no clue, I bought a few of the el cheapo ones at wal-mart. for like $2.50 comes with extra batteries. Its the one you find while standing in line (looks like a key chain with a small flashlight). got it because 3 batteries alone cost 5 bucks
. Been using one for over a week now and not used the extra batteries yet, but I know some batteries don't last. for me it's actually cheaper to buy another cheap pointer for the 6 batteries then the other way and just toss em in a drawer til one of the pointers dies.