Now that I am frequently opening the calculator to put new firmware types I enjoy having the 3D-printed Voyager battery covers. We have it for the original calculators (the small door for three button batteries) but we also have it for the new models (compatible from the 2007 model onwards, including HP12c and HP15c CE). This is an advantage because it does not need the ugly screw, and you can just open it and reset it if needed. Much more comfortable !!