Review on TalentCell 9V Lithium Ion Battery: High Capacity 500MAh Rechargeable Li-Ion Polymer Battery With Micro USB Charging Port - 1-Pack For Ultimate Convenience by Brian Wersching

The idea is really nice and I like the product.But it's slightly wider and slightly longer than regular battery.Basically it's plastic case seems to be exactly within the regular battery dimensions, but the transparent plastic heat shrink tube on top of it adds about 0.04"/1mm to width and height.I did read other comments about the dimensions before purchasing, but did not pay attention to it. Well, I still like it, but the size really matters. It turned out not to be as universal as I expected. I still buy regular batteries in addition to these.