Dual-layer cases are a good way to go if you want great protection, and don’t mind a little extra bulk when compared to a single-layer design.
The outer layer is hard plastic. This is designed to protect against drops and other types of damage. In keeps the phone from getting scratched. The inner-layer is made of rubber. This is designed to absorb impact. That said, the makers of this case did place importance on keeping it as thin as possible, even with their dual-layer design.
In short, it’s a well-built case that strikes a nice balance between thin and protective. Sure, there are cases out there that are more protective, but they are bulky. There are cases out there that are thinner, but they don’t offer the same degree of protection. This is a good way to go if you want something that’s somewhere in the middle.
They make the case for iPhone 4 and iPhone 4s, obviously, but they also sell it for iPhone 5.