Bests & Worsts Reviews from Amazon

I have a Carvin electric bass guitar that has, like thousands of other instruments, an electronics module powered by two 9V batteries. When my latest set of Duracells began to fade, I popped in a couple of these and expected to be back in business. Wrong! I got no sound at all. I did the "tongue test" to verify that the batteries were alive (yow!), and double-checked I'd installed them properly. Zilch. In desperation I put the old Duracells back in, and they worked just fine. I'm an electronics engineer and this was a problem I had to find. On close examination, here's the only possibility I can come up with: the metal + and - terminals of the Duracell battery project slightly farther from the battery's case than the Amazon's do. Apparently this allows them to reach the two contacts inside the bass. Also, the Amazon battery is a bit thicker than the Duracell, but I don't think that's the source of the problem. These would probably work fine in any application that has an actual battery clip that snaps onto the battery terminals. But for "drop-in" installations, you'd better verify that they work.