The most durable calculator I've ever had. If you have just one of these calculators, 1 is all you'll ever need provided you don't lose it. You'll likely lose it before it ever breaks. I own one from 7th grade that I have now owned for 15 years. I bought yet another one in college because I couldn't find my old one. Later on I found the old one again! So now I own 2. Come to think of it....where are my calculators?