This is the iPhone, the glass front and back, the metal edges, sturdy built.
It has the best design among all the iPhones, looks even better than the newer versions.
I have been using my phone for over 2.5 years and it still works with the latest OS(iOS9.2), not a single thing has been broken, this is definitely the best phone you will even find.
If you want to buy it today, I would not advise it just because the newer OS versions are coming with more features and require more RAM and processing power. So IPhone 4s is kind of outdated.
But I love the petite size, and the design.
Cheers