Ultra

By definition..Ultra means..."going beyond the usual limit; excessive; extreme"
Alas, not so in this case. I bought a dozen of these from a well known reputable source, two of which I used in my trusty wireless rodent..previously I had six months use from the top class, more costly ones, to find I got 6 weeks from these. A classic case of "you get what you pay for." Back to the expensive ones next time:-)