I actually had to replace the 2 little #319 batteries; the paper label was destroyed by unscrewing the battery sleeve in the pen top. The first battery came out fine, but there are 2 tiny access holes in the sides of the sleeve that I had to poke a needle into, to get the second little battery out. Replacements cost about $4 apiece! It is cheaper to buy a new HTC N-trig replacement pen than to buy new batteries. Even so, I have come to depend on the "double click to snip" feature with the pen; maybe I can buy these little rascals at wholesale...